Reducing Software Security Risk through an Integrated Approach
David P. Gilliam Caltech, Jet Propulsion Laboratory david.p.Gilliam@https://www.doczj.com/doc/6717034871.html,
John C. Kelly Caltech, Jet Propulsion Laboratory john.c.kellyw@https://www.doczj.com/doc/6717034871.html,
John D. Powell Caltech, Jet Propulsion Laboratory John.Powell@https://www.doczj.com/doc/6717034871.html,
Matt Bishop University of California at Davis bishop@https://www.doczj.com/doc/6717034871.html,
Abstract
This paper presents joint work by the California Institute of Technology’s Jet Propulsion Laboratory and the University of California at Davis (UC Davis) sponsored by the National Aeronautics and Space Administration Goddard Independent Verification and Validation Facility to develop a security assessment instrument for the software development and maintenance life cycle.
Vulnerabilities in operating systems and software applications render an otherwise secure environment insecure. Any operating system or application added to a secure environment that has exploitable security vulnerabilities affects the security of the whole environment. An otherwise secure system can be compromised easily if the system or application software on it, or on a linked system, has vulnerabilities. Therefore, it is critical that software on networked computer systems be free from security vulnerabilities.
Security vulnerabilities in software arise from a number of development factors; but these vulnerabilities can generally be traced to poor software development practices, new modes of attacks, mis-configurations, and unsecured links between systems.
A Software security assessment instrument can aid in providing a greater level of assurance that software is not exposed to vulnerabilities as a result of defective software requirements, designs, code or exposures due to code complexity and integration with other applications that are network aware.
This paper presents research on the generation of a software security assessment instrument to aid developers in assessing and assuring the security of software in the development and maintenance lifecycles. The research presented here is available at: https://www.doczj.com/doc/6717034871.html,/rssr. Keywords
Security Toolset, Vulnerability Matrix, Property-Based Testing, Model Checking, Security, Verification
1. Introduction
Software on networked computer systems must be free from security vulnerabilities. Security vulnerabilities in software arise from a number of development factors that can generally be traced to poor software development practices, new modes of attacks, mis-configurations, and unsecured links between systems. An otherwise secure system can be compromised easily if the system or application software on it, or on a linked system, has vulnerabilities.
Currently, there is a lack of Security Assessment Tools (SATs) for use in the software development and maintenance life cycle to mitigate these vulnerabilities. The National Aeronautics and Space Administration (NASA) has funded the Jet Propulsion Lab in conjunction with the University of California at Davis (UC Davis) to develop a software security assessment for use in the software development and maintenance life cycle.
The goal of the effort is the use of a formal analytical approach for integrating security into existing and emerging practices for developing high quality software and computer systems. The approach is to develop a security assessment instrument consisting of a collection of tools, procedures and instruments to support the development of secure software. Specifically, the instrument offers a formal approach for engineering network security into software systems and application throughout the software development and maintenance life cycles.
The security assessment instrument has three primary foci: a Vulnerability Matrix (VM), a collection of Security Assessment Tools (SAT) which includes the development of a Property-Based Testing (PBT) tool, and a Model-Based Verification (MBV) instrument.
The VM is a database maintained by UC Davis as part of the Database of Vulnerabilities, Exploits, and Signatures (DOVES) project. It contains a list of vulnerabilities, the associated platform/application, and the exploit signature fields.
The VM provides a searchable knowledge base from which properties may be extrapolated for use with PBT and MBV. This knowledge base can also accommodate the discovery of new attacks not yet seen on the internet, but which may be discovered through MBV techniques.
The SAT is a collection of tools and programs that can be used to check the security of software requirements, designs and source code. Each of the SAT’s includes a description of the tool and it use, its pros and cons, related tools, and where the particular tool can be obtained.
As part of the SAT, UC Davis is developing from a prototype a PBT tool. This PBT will slice software code looking for specific vulnerability properties. Property based testing is a tool that verifies properties against the code level implementation of a system. These properties are extracted from the VM, which may have grown due to properties being added through the use of MBV. Additionally, PBT is equipped with its own libraries that contain readily testable properties. Finally, used with the MBV, the PBT can provide verification of a model’s fidelity to the system in the MBV.
The MBV component of the research is a operational approach to perform verification of software designs for compliance to security properties. The Flexible Modeling Framework(FMF) approach is an innovative model checking approach that will facilitate the development and verification of software security models as composable components
Model based verification uses precise abstractions. It offers the ability to verify security properties over system models early in the life cycle – before an implementation exists. MBV can effectively identify security anomalies that have not been discovered as a result of a known network security attack. These new anomalies may then be added to the Vmatrix Anomalies that are found in early lifecycle phases through the examination of abstractions (models) can be preserved and later passed on to the PBT for verification at the code level.
The inception of this work was previously reported to IEEE WETICE Workshop on Enterprise Security.[1], 4th Annual Assurance Technology Conference at Glenn Research Center and the NASA OSMA Software Assurance Symposium ’01 sponsored by the NASA Goddard IV&V Facility. Three parts have been accomplished to date, the Vulnerability Matrix (Vmatrix), the initial collection of Security Assessment Tools (SATs), and the Property Based-Testing (PBT) instrument. A fourth part, the Model-Based Verification (MBV) instrument will be completed in April, 2002.
Assessments of high profile NASA systems believed to be vulnerable to attack will provide a metric to determine the effectiveness of these activities and prototypes. The security assessment instrument will be verified on a JPL/NASA Class A Flight Project to assess the approach and the viability of the security assessment instrument for assuring the security of software on critical networked systems.
2. Vulnerability Matrix (Vmatrix)
The VMatrix task was initiated to develop a searchable database containing a taxonomy of vulnerabilities and exposures and to catalogue them into libraries of properties that can be used in conjunction with the PBT and MBV instruments to assess the security of software code to assure that the software is free from the specified vulnerabilities and exposures. Of particular concern is that the properties of these vulnerabilities and exposures are not re-introduced during integration with operating systems or interoperability with other applications, nor in the introduction of upgrades to either the operating system or applications running on them.
Additionally, the information in the database is intended, in part, to provide network security professionals an understanding of the vulnerabilities and their exploits so they can better secure their systems. Equally important, it also provides developers with an understanding of the vulnerabilities and exposures in code that introduce security risks to software and systems. The intended goal is to enable developers to write more secure code and to provide a greater level of assurance that software code is not exposed to vulnerabilities when integrated with systems and other applications when used in a networked environment.
The Vmatrix, examines vulnerabilities and exposures and the methods used to exploit them. The VMatrix lists vulnerabilities and exposures along with their Common Vulnerabilities and Exposures (CVE) listing[2]. The VMatrix includes a brief summary and a description of the vulnerability or exposure, the affected software or operating system, how to detect the vulnerability or exposure and the fix or method for protecting against the exploit. Also included is catalogue information, keywords, and other related information as available, regarding the vulnerability or exposure. Interesting links, including links to Mitre with the CVE listing and the Ernst and Young website where vulnerabilities and exposures are ranked by severity and frequency among other factors, are also provided.
The VMatrix led to the development and extension of a database controlled and maintained by UC Davis, the Database of Vulnerabilities, Exploits, and Signatures, (DOVES). DOVES contains additional vulnerabilities and exposures beyond that which is now contained in the VMatrix.
The Vmatrix, the DOVES database along with the SATs (discussed below) are available from websites at JPL and UC Davis which can be reached from: https://www.doczj.com/doc/6717034871.html,/rssr.
3. Security Assessment Tools (SATs)
The Security Assessment Tools are free tools that have been developed and collected for use in testing and assuring the security of operating systems and software. This collection is provided as a list on the web sites noted above. The SATs are a listing of tools that contain a brief summary stating the purpose of the tool, where the tool can be obtained, and their use along with pros and cons of each of the tools. Also provided, is a list of similar tools or alternative tools, and a classification of each tool. A journal paper, “A Classification Scheme for Security Tools,” provided on the SATs web page, discusses a classification scheme of these security related tools and their usage.
A more complete description of the tools and a discussion of how to use each of the tools is currently being developed. Additional SATs are being collected as they become available to include in the current list.
The SATs will be categorized and cross-referenced to alternate tools so that code developers, system administrators, and network and computer security professionals can have a central location to search for specific tools for use in writing secure software code and securing computer systems.
4. Property-Based Testing
The role of property-based testing is to bridge the gap between formal verification and ad hoc verification. This provides a basis for analyzing software without sacrificing usefulness for rigor, yet capturing the essential ideas of formal verification. It also allows a security model to guide the testing for security problems
Property-based testing [3] is a technique for testing that programs meet given specifications. The tester gives the specifications in a language that ties the specification to particular segments of code. The specification has assertions, which indicate changes in the security state of the program, and properties, which describe a specific set of states that are considered secure in this context. The idea is to ensure that the properties always hold. The tester consists of two parts. The instrumenter inserts statements into the source code that emit assertions about the current state of execution. The execution monitor takes that information as input and determines if the current state of execution violates any of the properties. If so, the program has a security flaw. The instrumenter, execution monitor, and any libraries of desireable security properties make up the Tester's Assistant (TA).[4]
PBT Model
Figure 1
Our goal was to develop the TA to test programs written in C++ code for the UNIX environment. However, the TA task has been changed to test programs written in JAVA instead. This eliminates some problems such as pointer aliasing (because JAVA does not have it). It also introduces some problems, because certain system functions (such as the printing functions) are not written in JAVA. If the call to such a function is instrumented, the native code instrumented, or the statements must surround the call to the routine instead of being invoked as the first instruction in the routine. The first would require developing a much more general instrumenting tool, so we opt for the second. When the method being invoked is computed at runtime, the complexity of the wrapping instatements is considerable,
We have also modified the TASPEC specification language[5] to clarify ambiguities uncovered by our testing. For example, consider the assertions authenticated (bob), password (bob), password (alice) are present in the database. The instrumented program puts out the property authenticated (x) and password (x). Does the execution monitor report a violation, because there exists one value for x such that the property fails, or does it say the property is satisfied, because there exists one value of x such that the property holds? We have chosen the latter, but one could equally well choose the former. The only difference that would cause is in the writing of specifications.
5. Model-Based Security Specification and Verification
Model based specification and verification make use of discrete finite models to verify compliance of the model to desired properties; in this case, software/network security properties. Network security properties often focus on characteristics that are manifested though the operation of multiple software applications and systems operating concurrently with an attacking process. The concurrent nature of the systems results in an operational space that is too large to effectively verify security properties through traditional testing of the implementation. Further, vulnerabilities introduced in the early phases of the development lifecycle are difficult or impossible to remove in later phases when an implementation is being tested. This results in the addition of cumbersome workarounds and “patches” to secure the software system. Model based verification offers the opportunity to verify properties early in the life cycle, providing a clearer understanding of the vulnerability issues within the system before an implementation exists.
Figure 2
Processors P1, P2
Figure 3
Model checkers automatically explore all paths in a finite state space from a given start state in a computational tree. The objective is to verify system
properties over all possible scenarios within a model. Model Checkers differ from more traditional heavyweight formal techniques in that:
? Model checkers are operational as opposed to
deductive
? Model checkers provide counter examples when
properties are violated (counter examples) ? Their goal is oriented toward finding errors as
opposed to proving correctness since the model is an abstraction of the actual system
Figure 4
Model based verification techniques, such Model Checking, are not without drawbacks. Among them are the ability to model a system with a high degree of fidelity in a timely manner while the system evolves. This is particularly problematic in the earliest stage of development such as requirements and high-level design when the system definition is most volatile. This lack of agility limits an analysts ability to maintain an up to date model that and minimize the latency between the introduction of errors and their discovery.
A limitation specific to model checking is the state space explosion problem. Similar to the growth of the growth of the operational space mentioned above, the state space that a model checker must search to verify properties grows at an exponential rate as the model becomes more detailed. As shown in figures 2 through 4
the state space grows at a rate of m n
where m is the range of possible values a variable may assume and n is the number of variables in the model. Despite the use of modeling techniques such as abstraction and homomorphic reduction it is infeasible to verify all but the most simplistic software systems in their entirety though model checking.
An innovative verification approach that employs model checking as its core technology is offered as a means to bring software security issues under formal control early in the life cycle while mitigating the drawbacks discussed above. The Flexible Modeling Framework (FMF) is an approach that employs:
Process P1 Process P2 . . .
? A system for building models in a component based manner to cope with system evolution in a
timely manner
? A compositional verification approach to delay the effects of state space explosion and allow property
verification results to be examined with respect to
larger, complex models in an indirect manner.
Modeling in a component-based manner involves the building of a series of small model, which will later be strategically combined for system verification purposes. This correlates the modeling function with modern software engineering and architecture practices where by a system is divided into major parts, and subsequently into smaller detailed parts, and then integrated to build up a software system. An initial series of simple components can be built when few operational specifics are known about the system. However these components can be combined and verified for consistency with properties of interest such as software security properties. As the system evolves only the affected components need be modified. Further by retaining knowledge from previous verifications the effort of re-verifying properties may be reduced significantly. This will result in a decreased cycle time for verification of model updates thus improving the timeliness of the formal verification results. As more is learned about the system’s specific manner of accomplishing its task(s) the affected model components can be:
? Modified to reflect the more detailed approaches developed during the design phase.
? Segmented into its own series of components when the complexity of the high level component
begins to exhibit state space explosion problems.
The approach of compositional verification used in the FMF seeks to verify properties over individual model components and then over strategic combinations of them. The goals of this approach are to: 1) infer verification results over systems that are otherwise to large and complex for model checking from results of strategic subsets (combinations) while minimizing false reports of defects. 2) Retain verification results from individual components and combination to increase the efficiency subsequent verifications and ultimately aid in the strategic combination selection process. The FMF verification process begins determining which model components are safe and unsafe with respect to the property in question. Then, the strategic combination process seeks to build up relationships between components. Figure 5 shows an example where the components C1and C3are safe with respect to some security property while the states C2 and C4 are unsafe. Relationships between C1 and C2 as well as C3 and C4 are shown. Since C2 is individually unsafe, C1 is individually safe and the combination C1 and C2 is safe, C1 is said to mitigate C2. Conversely C3 is safe and C4 is unsafe and the combination of the two components is unsafe. In this case C4 is said to undermine C3. It bears noting that two components that are labeled individually safe may produce and unsafe security condition when combined and vise versa.
each property will allow future verifications of the property to be accomplished by noting the relationships that were used to make earlier verification inferences and only re-verifying the relationships affected by a component change or addition.
This approach is currently under development and shows promise for early life cycle detection of security vulnerabilities. The approach may be generalized and/or tailored in future work for applicability to non-security domains such as safety.
6. Instrument Integration
The various parts of the Security Assessment Instrument can be used separately or in combination (See Figure 6) providing the additional benefits of:
? Reduced rework to identify security properties
? Increased confidence in the system through verification at multiple times during the
development and maintenance lifecycle ? One tool is capable of verifying the input and output of another tool in the instrument
? Finding additional attacks yet to be seen in the wild (attacks that have not yet been seen outside
of a laboratory environment) and test for their
viability and severity
6.1. Vulnerability Matrix (VMatrix)
The vulnerability matrix provides a searchable knowledge base from which properties may be extrapolated for use with PBT (See Section 6.1.) and Model Based Verification (MBV) (See Section 6.3.). This knowledge base can also accommodate the discovery of new attacks not yet seen in the wild that may be discovered through MBV techniques.
6.2. Property Based Testing (PBT)
Property based testing is a tool that verifies properties against the code level implementation of a system. These properties are extracted from the VMatrix (See Section 6.1.), which may have grown due to properties being added through the use of MBV (See Sec 6.3.). Additionally, PBT is equipped with its own libraries that contain readily testable properties. Finally, used with the MBV, the PBT can provide verification of a model’s fidelity to the system in the MBV.
6.3. Model Based Verification (MBV)
Due to the fact that Model based verification uses precise abstractions; it offers the ability to verify security properties early in the life cycle – before an implementation exists. The MBV can effectively identify and notify the VMatrix of security anomalies that are not yet seen in the wild (See Sec 6.1.). Anomalies found early in the lifecycle by examining abstractions can later be passed on to the PBT for verification at the code level (See Sec 6.2.).7. Conclusion
The four parts of the integrated approach for detecting security vulnerabilities in software form a coherent technique for examining systems for software security flaws. Each part can be used independently or in conjunction with another. When used in conjunction with each other, synergistic benefits are leveraged to classify and understand security properties for modeling and testing. The VMatrix and model-based checking provide the properties that the software must meet; the property-based tester checks that implementations do indeed meet these properties. The V Matrix forms the beginning of a library of properties. Property-based testing requires properties expressed in TASPEC to test against. Training in the writing of more secure programs flows directly from the library of security properties. Placing these properties in the context of a particular system environment is an important part of improving the quality of software and systems.
8. Acknowledgements
The research described in this paper is being carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration, and the University of California at Davis under a subcontract with the Jet Propulsion Laboratory, California Institute of Technology.
9. References
[1] D. Gilliam, J. Kelly, M. Bishop, “Reducing Software Security Risk Through an Integrated Approach,” Proc. of the Ninth IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises (June, 2000), Gaithersburg, MD, pp.141-146.
[2] Published and maintained by Mitre. The CVE listing can be found at: https://www.doczj.com/doc/6717034871.html,/
[3] G. Fink, M. Bishop, “Property Based Testing: A New Approach to Testing for Assurance,” ACM SIGSOFT Software Engineering Notes22(4) (July 1997).
[4] M. Bishop, "Vulnerabilities Analysis," Proceedings of the Recent Advances in Intrusion Detection (Sep. 1999).
[5] J. Dodson, "Specification and Classification of Generic Security Flaws for the Tester’s Assistant Library," M.S. Thesis, Department of Computer Science, University of California at Davis, Davis CA (June 1996).
Figure6
[6] J. R. Callahan, S. M. Easterbrook and T. L. Montgomery, "Generating Test Oracles via Model Checking," NASA/WVU Software Research Lab, Fairmont, WV, Technical Report # NASA-IVV-98-015, 1998.
[7] P. E. Ammann, P. E. Black and W. Majurski. “Using Model Checking to Generate Test Specifications,” 2nd International Conference on Formal Engineering Methods (1998) pp. 46-54.
[8]G. Lowe. Breaking and Fixing the Needham-Schroeder Public Key Protocol Using CSP and FDR. In TACAS96, 1996.
[9] W. Wen and F Mizoguchi. Model checking Security Protocols: A Case Study Using SPIN, IMC Technical Report, November, 1998.
2013年安徽省初中毕业学业语文考试卷 安徽省阜阳市颍泉区邵营中学王海军 一、语文积累与综合运用 (35分) 1.默写古诗文中的名句名篇。(10分） (1)补写出下列名句中的上句或下句。(任选其中 ．．．．6．句．) ①择其善者而从之，。（《论语》） ②，若出其里。(曹操《观沧海》) ③苔痕上阶绿，。(刘禹锡《陋室铭》) ④无可奈何花落去，。(晏殊《淀溪沙》) ⑤，处江湖之远则忧其君。(范仲淹《岳阳楼记》） ⑥，柳暗花明又一村。(陆游《游山西村》) ⑦夕阳西下，。(马致远《天净沙·秋思》) ⑧，宫阙万间都做了土。(张养浩《山坡羊·潼关怀古》 (2)默写白居易《钱塘湖春行》的后四句 ．．．。 2、阅读下面的文字，完成(1)-(4)题。(9分) 古往今来，人们都在编织着梦想与希jì。如果说梦想是天边的星晨，永恒地照亮匆匆的人生，那么，现实就是脚下的土地，真实地记录着行走的足迹。人，既不能生活在华而不实的梦想里，也不要沉nì于喧嚣纷扰的现实中。在人生的道路上，我们要一边种植梦想，，随时采撷，收获希望。 (1)根据拼音写出相应的汉字，给加点的字注音。 希jì( ) 沉nì( ) 喧嚣．( ) (2)文中有错别字的一个词是“”，这个词的正确写法是“”。 ①“华而不实”中，“华”的意思是。“采颇”的意思是。 ②根据文意，仿照文中画线的句子，在横线处填上一句恰当的话。 3、运用你课外阅读积累的知识，完成(1)~(2)题。(4分) (1)下面一段文字节选自《骆驼祥子》，读一读，指出A、B两处的人物是谁。 A心里有数儿。他晓得祥子是把好手，即使不拉他的车，他也还愿意祥子在厂子里。有祥子在这儿，先不提别的，院子与门口永远扫得干干净净。B更喜欢这个傻大个儿，她说什么，祥子老用心听着，不和她争辩；别的车夫，因为受尽苦楚，说话总是横着来；她一点不怕他们，可是也不愿多搭理他们；她的话，所以，都留给祥子听。 (2)安徒生笔下，卖火柴的小女孩借着火柴的亮光，看见了温暖的、喷香的烤鹅、美丽的圣诞树、和蔼的。 4、九年级开展以“文明出行”为主题的综合实践活动。活动中有一些问题，请你参与解决。（12分） (1)下面是同学们在活动中整理的《闯红灯原因统计表》，请你用简洁的语言表述其中是信息。(不．得出现数 ．．．．字．)
“的、地、得”用法分析及练习（后附答案） 一、的、地、得用法分析： “的”后面跟的都是表示事物名称的词或词语，如：敬爱的总理、慈祥的老人、戴帽子的男孩、珍贵的教科书、鸟的天堂、伟大的祖国、有趣的情节、优雅的环境、可疑的情况、团结友爱的集体、他的妈妈、可爱的花儿、谁的橡皮、清清的河水...... “地”后面跟的都是表示动作的词或词语，如：高声地喊、愉快地唱、拼命地逃、疯狂地咒骂、严密地注视、一次又一次地握手、迅速地包围、沙沙地直响、斩钉截铁地说、从容不迫地申述、用力地踢、仔细地看、开心地笑笑......” “得”前面多数是表示动作的词或词语，少数是形容词；后面跟的都是形容事物状态的词或词语，表示怎么怎么样的，如：走得很快、踩得稀烂、疼得直叫唤、瘦得皮包骨头、红得发紫、气得双脚直跳、理解得十分深刻、乐得合不拢嘴、惊讶得目瞪口呆、大得很、扫得真干净、笑得多甜啊...... 二、的、地、得用法补充说明： 1、如果“de”的后面是“很、真、太”等这些词，十有八九用“得”。 2、有一种情况，如“他高兴得一蹦三尺高”这句话里，后面的“一蹦三尺高”虽然是表示动作的，但是它是来形容“高兴”的程度的，所以也应该用“得”。
三、的、地、得用法总结： 1、“的”前面的词语一般用来修饰、限制“的”后面的事物，说明“的”后面的事物怎么样。结构形式一般为：修饰、限制的词语+的+名词。 2、“地”前面的词语一般用来形容“地”后面的动作，说明“地”后面的动作怎么样。结构方式一般为：修饰、限制的词语+地+动词。 3、“得”后面的词语一般用来补充说明“得”前面的动作怎么样，结构形式一般为：动词（形容词）+得+补充、说明的词语。 四、的、地、得用法例句： 1. 蔚蓝色的海洋，波涛汹涌，无边无际。 2. 向日葵在微风中向我们轻轻地点头微笑。 3. 小明在海安儿童公园玩得很开心。 五、“的、地、得”的读音： “的、地、得”是现代汉语中高频度使用的三个结构助词，都起着连接作用；它们在普通话中都各自有着各自的不同的读音，但当他们附着在词，短语，句子的前面或后面，表示结构关系或某些附加意义的时候都读轻声“de”，没有语音上的区别。 但在书面语中有必要写成三个不同的字，这样可以区分他们在书面语用法上的不同。这样做的好处，就是可使书面语言精确化。
连词 连词是用来连接词与词、词组与词组、句子与句子，表示某种逻辑关系的虚词。连词可以表并列、承接、转折、因果、选择、假设、比较、让步、递进、条件、目的等关系。一般说来，连词有很多是由副词、介词发展而来的；很多副词、介词又是由动词发展而来。所以动词、介词、连词需要区别。 和 =跟、=与、=及、=同<方>。表示并列关系、联合关系。 车上装的是机器和材料。他的胳膊和大腿都受伤了。工人和农民都是国家的主人。工业与农业。批评与自我批评。我同你一起去。图书、仪器、标本及其他。（注意：用“及”连接的成分多在词义上有主次之分，主要成分放在“及”的前面） 以及 连接并列的词或词组（“以及”前面往往是主要的）：院子里种着大丽花、矢车菊、夹竹桃以及其他的花木。 既=既然 既来之，则安之。既然他不愿意，那就算了吧。既然知道做错了，就应该赶紧纠正。你既然一定要去，我也不便阻拦。既要做，就一定要做好。既然这样，还不去做？用在上半句话里，下半句话里往往用副词就、也、还跟他呼应，表示先提出前提，而后加以推论。 既然。。。就。。。既然。。。也。。。既然。。。还。。。 继而=既而 先是惊叹，既而大家一起欢呼起来。人们先是一惊，继而哄堂大笑。先是一个人领唱，继而全体跟着一起唱。表示紧随在某一情况或动作之后。 而 1、连接动词、形容词、词组、分句。 （1）连接语意相承的成分。伟大而艰巨的任务。战而胜之，取而代之，我们正从事一个伟大的事业，而伟大的事业必须有最广泛的群众的参加和支持。 （2）连接肯定和否定相互补充的成分：此种花香浓而不烈，清而不淡。马克思主义叫我们看问题不要从抽象的定义出发，而要从客观存在的事实出发。有转折的意思。 （3）连接语意相反的成分，表转折：如果能集中生产而不集中，就会影响改进技术、提高生产。 （4）连接事理上前后相因的成分：因困难而畏惧而退却而消极的人，不会有任何成就。 2、有“到”的意思。一而再，再而三。由秋而冬。由南而北。 3、把表示时间、方式、目的、原因、依据等的成分连接到动词上面。匆匆而过、挺身而出、为正义而战、因公而死、视情况而定、三十而立。 而且 表示更进一步，前面往往有“不但、不仅”跟它呼应：性情温和而且心地善良。他不仅会开汽车，而且会修汽车。不但战胜了各种灾害，而且获得了丰收。 因而=因此 表示结果。下游河床狭窄，因而河水容易泛滥。 因为 常跟所以连用，表示因果关系。因为今天事情多，所以没去成。 何况 用反问的语气表示更进一层的意思。这么多事情一个人一天做完是困难的，何况他又是新手。他在生人面前都不习惯讲话，何况要到大庭广众之中呢？（even）
初中阶段主要句型的用法 1. It's time to (for) .... 表“时间到了；该干…的时间了”之意。 It's time to go home. It's time for school. 注意：to的后面接动词短语，而for的后面接名词。 2. It's bad (good) for ... 表示“对…有害（有益）的”含义。 Please don't smoke. It's bad for your health. Please take more exercise. It's good for your health. 3. be late for (school) 是“上学（迟到）”之意。for后面还可以接meeting或class。He was late for school this morning. Don't be late for class, please. 4. had better do / not do sth. 表示“最好做/不做某事”之意。 You had better put on the coat when you go out. It's cold outside. We had better stop to have a rest. 注意：用had better时，后面一定要直接跟动词原形，决不能加to do sth. 否定一定用在第二个动词之前，是动词不定式的否定式。 5. be (feel) afraid of ... 表示“恐怕”，“害怕…”之意。 He is afraid of snakes. Mary feels afraid of going out alone. 6. enjoy doing sth. 是“喜欢（爱好）做某事”之意，doing是动名词作动词enjoy 的宾语。enjoy有欣赏之意。 Are you enjoy living in Beijing? Do you enjoy listening to music? 7. stop doing sth. 停止做某事 stop to do sth. 停下来做某事 It's time for class. Stop talking, please. When she saw me, she stopped to talk with me. 8. Let (make) sb. do 让（使）某人做某事。 Let's go to school. Father made his son clean the room again. 注意：当make sb. do sth. 用于被动语态时，第二个动词前面就一定要加to 了。如： His son was made to clean the room again. he was made to work twelve hours a day in the past. 9. like to do / like doing sth. 是“喜欢做某事”之意。 like to do sth. 是表示比较具体的喜欢做某事；like doing sth. 是表示宠统的喜欢做某事。如： I like to swim in the swimming pool. 我喜欢在游泳池中游泳。（喜欢的具体的地方游泳） I like swimming. 我喜欢游泳（只讲喜欢这项运动） 10. ask (tell) sb. to do. (not to do) sth. 请（让）某人（不）做某事 Jim asked his mother to help him with his lessons. When did you tell him not to shout loudly?
2 0 1 3 年安徽省初中毕业学业考试 物理 题号一二三四总分 得分 注意事项： 1．本卷共四大题 23 小题，满分 90 分。物理与化学的考试时间共 120 分钟。 2．本卷试题中 g 值均取 10N／kg。 一、填空题（每空 2 分，共 26 分；将答案直接写在横线上，不必写出解题过程）1．小林坐在行驶的火车上，以他乘坐的火车为参照物，他是（选填“运动” 或“静止”）的。 2．商场里的保洁员在拖过地后，常用电扇对着地面吹，这样做的目的是通过加快空气流动 来加快（填物态变化的名称），使地面尽快变干， 3．小明在一次测量体温时，体温计的示数如图所示，则他的体温为℃。 ℃ 35 36 37 38 39 4041 42 第 3 题图 4．古诗“花气袭人知骤暖”的意思是，从花的芳香气味变浓可以知道周边的气温突然升高。 从物理学的角度分析，这是因为温度越高，。 5．小强在立定跳远起跳时，用力向后蹬地，就能获得向前的力，这是因为物体间力的作用 是的。离开地面后，由于，他在空中还能继续向前运动。 6．如图，能说明发电机工作原理的是图（选填“甲”或“乙”）。 图甲图乙 第 6 题图
7．如图，静止在花朵上的一种叫“全碳气凝胶”的固体材料，它是我国科学家研制的迄今 为止世界上最轻的材料。一块体积为100cm3的“全碳气凝胶”的质量只有0.016g ，则它的 密度为kg/m3。 第 7 题图第 8 题图第 9 题图 8．我国设计的“中华月球车”今年将登陆月球，图为该车的模型。物体在月球表面附近受 到的重力仅为在地球表面附近所受重力的1/6 ，月球车的质量为 120kg，它在月球表面附近 受到的重力为N。若它在月球表面上方竖直下落4m，重力对它做的功为J。 9． 2013 年 5 月，象征“和平、友爱和快乐”的巨型大黄鸭在香港与游客见面，图为大黄鸭 漂浮在海面上的情景。大黄鸭的质量约为 600kg，海水的密度取1.0103 kg / m 3，它浸在水 中的体积约为m3。 L2 10．如图，小灯泡L1和 L2均标有“，0.3A ”字样，AB两端的电压U A B ＝。开关 S 断开时，通过L2的电流为A。闭合开关 S，两只小L1S 灯泡消耗的总电功率为W 。 U 第 10 题图 二、选择题（每小题 3 分，共 21 分；每小题给出的四个选 项中，只有一个选项符合题意，请把符合题意的选项序号填入下列表格内，答案 ．．．．．．． 未填入表格内的不能得分） 题号11121314151617 答案 11．下列各图描述的实验中，用来说明声音的传播需要介质的是 A．发声的音叉激B．音叉发出的声音C．钢尺伸出桌边的长度D．抽取玻璃罩内的空气，起水花越响，乒乓球被弹开变短，振动时声音音调变听到罩内的音乐声减小 的越远高
and的用法及含义 And是英语中一个普通的连词，然而and并非只作并列连词用，它还具有一些不太常见的表达方式和意义，应根据上下文的特殊环境，作出判断才能准确理解其用法和意思。 1．and作并列连词，译为“和、并且”等，当连接三个以上的并列成分时，它放在最后一个成分之前，其余用逗号分开，例如： He bought a book and a pen．他买了一本书和一支笔。 Solid，liquid and gas are the three states of matter．固态、液态和气态是物质的三种状态。 2．名词+and+名词，若这种结构表示一个概念时，and+名词相当于介词with+名词，译为“附带、兼”的意思，例如： Noodle and egg is a kind of delicious food．（and egg=with egg）鸡蛋面是一种美味食物。 Whose is this watch and chain？（and chain＝with chain）这块带表链的手表是谁的？ 3．名词复数+and+同一名词的复数，强调连续或众多的含义。例如： There are photos and photos．照片一张接着一张。 They saw film hours and hours last week．上星期他们一小时接一小时地看电影。 4．形容词+and+形容词，这种结构形似并列，实际并非并列结构。例如： This roon is nice and warm（＝nicely warm）． The coffee is nice and hot（=thoroughly hot）． 5．用and连接动词的用法：and+动词作目的状语。动词go（come，stop等）＋and+动词，此时，and+动词相当于in order to+动词，例如： ①I'll go and bring back your boots，（go and bring back=go in order to bringback）我去把你的靴子拿来。 ②and+动词，起现在分词的作用，表示方式或伴随情况。例如： He sat and waited．（and waited=waiting）他坐着等。 ③and+同一动词表示动作长时间地“继续”或“重复”，例如：
期末复习提纲（十） Un it 10 By the time I got outside, the bus had already left. 重点词组与句型： 1. take a shower 2.get in the shower 3.get up 4.get outside 5.get to school 6.1 eave sth.+ 地点 7.get back to sp. 8.start teach ing 9.wake up late 10.be late for 11.go off 12.wait for https://www.doczj.com/doc/6717034871.html,e out 14.have some breakfast 15.run off 16.get there 17.on time https://www.doczj.com/doc/6717034871.html,e by 19.give sb. a ride 20.bri ng sth. to sp. 21.break dow n 22.show up 23. get dressed 24.stay up all night 25. invite sb. to do sth. / invite sb. to sp. 26. by the time 27.happa n to sb. 28. a costume party 29.thousa nds of 30.h un dreds of * (31.flee from sp. 32. April Fool ' s DOyB.stop doing sth. 34.as …as one can 35. fool sb. 36.ask sb. to do sth. 37.both…and 38.an hour later 39. get married 40.play a joke on sb) 40. By the time I got up, my brother had already gotte n in the shower. 41. By the time she got up, her brother had already gone into the bathroom. 42. By the time she went outside, the bus had already gone. 43. By the time she got to class, the teacher had already started teach ing. 44. Whe n she got to school, she realized she had left her backpack at home. 45. By the time I got back to school, the bell had rung. 46. My alarm clock didn ' t go off. 47.1 took a quick shower, and had some breakfast, and the n ran off to the bus stop. * (48.Have you ever forgotte n to bring your homework to school? 49.Wells was so convincing that hun dreds of people believed the story. 50.She was thrilled, because she wan ted to get married. 语法： 过去完成时。 练习： 一、根据句子意思和所给首字母提示，用适当单词完成句子。 1. Bad luck. I missed the early bus because I o ______ this morni ng. 2. Perhaps he ' ll dress himself up as a clown in the c _________ party. 3. You must be e ________ a fter swimmi ng for along time. Come and have a rest.
２０13年安徽省中考英语试卷 第一部分听力（共五大题,满分３0分) I.关键词语选择（共５小题；每小题1分,满分5分) 你将听到五个句子。请在每小题所给的Ａ、Ｂ、C 三个选项中选出一个你所听到的单词或短语。每个句子读两遍。 1.Ａ. traｄｅ B.ｔrｉp C. tｒain ２． A. warn B．wash C.ｗａtch ３. A. ｓofｔ B. ｓaｆe Ｃ．sａme ４. Ａ. ticｋet B. bａskeｔＣ. pｒｅsｅnｔ' ５. A. ｋeep ｏff B．gｅt oｆfＣ．turn off Ⅱ.短对话理解（共10小题；每小题１分,满分10分）你将听到十段对话，每段对话后有一个小题。请在每小题所给的Ａ、Ｂ、C三个选项中选出一个最佳选项。每段对话读两遍。 6. Wｈat is the ｍａn's job? 7.Wｈat is the man ｇoinｇto ｄo? ８.Whichａnimａｌｉｓｍｅnｔｉoｎeｄiｎtｈe ｃonvｅrsaｔｉon? 9．Wｈat spｏrt wｉll tｈe ｍaｎdo this Saturdaｙ? １0. Ｗhaｔis the mａn looking ｆor？ 1１. Whｅre can the wｏman parｋthe ｃａｒ? A. Ｂy the road. B. In the buiｌdiｎg．Ｃ. Beｈindｔhe builｄiｎｇ. 12．How doｅｓthｅman ｇoｔｏｗorｋthese days？ A. Bｙcar. B. By taxi.C．Bｙｂike. １３. Whａｔdｏｅs the mａｎmｅan? Ａ．He likes hｉs job. B. Ｈe hates hｉs jｏb. C.Ｈｅoftｅn ｌoses jｏbs. 1４.Hoｗmuｃh wilｌｔhe man pay?
2013年安徽省初中毕业学业考试 数 学 本试卷共八大题，计23小题，满分150分，考试时间120分钟. 一、选择题（本大题共10小题，每小题4分，满分40分）每小题都给出代号为A 、B 、C 、D 的四个选项，其中只有一个是正确的，请把正确选项的代号写在题后的括号内，每一小题，选对得4分，不选，错选或选出的代号超过一个的（不论是否写在括号内）一律0分 1．-2的倒数是（ ） （A ）- 21 （B ）2 1 （C ） 2 （D ）—2 2．用科学记数法表示537万正确的是（ ） （A ）537×104 （B ）5.37×105 （C ）5.37×106 （D ）0.537×107 3．图中所示的几何体为圆台，其主（正）视图正确的是（ ） 4．下列运算正确的是（ ） （A ）2x +3y =5xy （B ）5m 2·m 3=5m 5 （C ）()2 22 a b a b -=- （D ）m 2·m 3=m 6 5．已知不等式组? ??≥+>-0103x x 其解集在数轴上表示正确的是（ ） 6．如图，AB ∥CD ，∠A +∠E =75°，则∠C 为（ ） （A ）60° （B ）65° （C ）75° （D ）80°
7．目前我国已建立了比较完善的经济困难学生资助体系，某校去年上半年发放给每个经济困难学生389元，今年上半年发放了438元.设每半年．．．发放的资助金额的平均增长率为x ，则下面列出的方程中正确的是（ ） （A ）4382(1)x +=389 （B ）3892(1)x +=438 （C ）389(12)x +=438 （D ）438(12)x +=389 8．如图，随机闭合开关K 1、K 2、K 3中的两个，则能让两盏灯泡同时发光的概率为（ ） （A ）61 （B ）31 （C ）21 （D ）3 2 9．图1所示矩形ABCD 中，BC =x ，CD =y ，y 与x 满足的反比例函数关系如图2所示，等腰 直角三角形AEF 的斜边EF 过C 点，M 为EF 的中点，则下列结论正确的是（ ） （A ）当x =3时，EC ＜EM （B ）当y =9时，EC ＞EM （C ）当x 增大时，EC ·CF 的值增大. （D ）当y 增大时，BE ·DF 的值不变. 10．如图，点P 是等边三角形ABC 外接圆⊙O 上的点，在以下判断中，不正确．．．的是（ ） （A ）当弦PB 最长时，APC △是等腰三角形 （B ）当APC △是等腰三角形时，PO ⊥AC （C ）当PO ⊥AC 时，∠ACP =30° （D ）当∠ACP =30°，PBC △是直角三角形
一．time的短语 from time to time 有时 on time 准时, in time 及时; all the time 始终,一直; at the same time 同时， ahead of time提前 at no time 绝不 some time一段时间 sometime“在某一时候”。可用来指过去或将来 sometimes (at times, from time to time) “有时，不时” at a time （a time） at one time （once）
at times ( sometimes) in no time （immediately）立刻,马上; have a good/nice time (enjoy oneself) “过的愉快 for the time being “暂时” Many a time/many times 多次 take one’s time从容 kill time消磨时间 【活学活用】选出与画线部分意思相同或相近的选项 1. Jim comes to visit us from time to time. That’s always the happiest time for the family. A.on time B. sometime C. at times D. some times
2．At no time _____study though __ ___great progress. A. should we give up; we have made B. shouldn’t we give up; we have made C. we should give up; we have made D. we shouldn’t give up; have we made 3.---When shall we visit the Science Museum?” ---_________ next week.” A.Sometime B. Sometimes C. Some time D. Sometimes 答案：1. C2.A 3A 二．time相关从属连词高考常考点 1. every time / each time每次 Every time I call on him, he is out.
2013年安徽省初中毕业学业考试数学试卷及答案 一、选择题：（每小题4分，满分40分） 1.-2的倒数是（ ）A.- 21 B.2 1 C.2 D.-2 2.用科学记数法表示537万正确的是（ ） A.537×104 B.5.37×105 C.5.37×106 D.0.537×107 3.图中所示的几何体为圆台，其主（正）视图正确的是（ ） 4.下列运算正确的是（ ） A.2x+3y=5xy B.5m 2·m 3=5m 5 C.(a-b)2=a 2-b 2 D.m 2·m 3=m 6 5.已知不等式组? ? ?≥+?-010 3x x 其解集在数轴上表示正确的是（ ） 6.如图，AB ∥CD,∠A+∠E=750 ,则∠C 为（ ）A.600 B.65 C.750 D.800 7.目前我国已建立了比较完善的经济困难学生资助体系。某校去年上半年发给每个经济困难学生398元，今年上半年发放了438元，设每半年．．．发放的资助金额的平均增长率为x ，则下面列出的方程中正确的是（ ） A.438(1+x)2 =389 B.389(1+x)2 =438 C.389(1+2x)=438 D.438(1+2x)=389 8.如图，随机闭合开关K 1,K 2,K 3中的两个，则能让两盏灯泡同时．．发光的概率为（ ） A. 61 B.31 C.21 D.3 2 K 2 K 3 K 1 L 1 L 2 B A D C 第3 A B C D E A B C D F
过点C ，M 为EF 的中点，则下列结论正确的是（ ） A.当x=3时，EC ＜EM B.当y=9时，EC ＞EM C.当x 增大时，EC ·CF 的值增大 D.当y 增大时，BE ·DF 的值不变 10.如图，点P 是等边三角形ABC 外接圆⊙O 上点，在以下判断中，不正确．．．的是（ ） A.当弦PB 最长时，△APC 是等腰三角形 B.当△APC 是等腰三角形时，PO ⊥AC C.当PO ⊥AC 时，∠ACP=300 D.当∠ACP=300 时，△BPC 是直角三角形 二、填空题： 11.若x 31 在实数范围内有意义，则x 的取值范围是 12.分解因式：x 2 y-y= 13.如图，P 为平行四边形ABCD 边AD 上一点，E,F 分别是PB,PC 的中点，△PEF,△PDC,△PAB 的面积分别为S,S 1,S 2,若S=2，则S 1+S 2= 14.已知矩形纸片ABCD 中，AB=1，BC=2，将该纸片折叠成一个平面图形，折痕EF 不经过A 点（E,F 是该矩形边 界上的点），折叠后点A 落在点A / 处，给出以下判断： ①当四边形A / CDF 为正方形时，EF=2;②当EF=2时，四边形A / CDF 为正方形； ③当EF=5时，四边形BA /CD 为等腰梯形；④当四边形BA / CD 为等腰梯形时，EF=5. 其中正确的是 （把所有正确结论的序号都填在横线上） · O A B C P A B D P F E 第13题图 M 第9题 图1 第9题 图2
标点符号用法 一、标点符号 标点符号：辅助文字记录语言的符号，是书面语的有机组成部分，用来表示语句的停顿、语气以及标示某些成分（主要是词语）的特定性质和作用。 句子：前后都有较大停顿、带有一定的语气和语调、表达相对完整意义的语言单位。 复句：由两个或多个在意义上有密切关系的分句组成的语言单位，包括简单复句（内部只有一层语义关系）和多重复句（内部包含多层语义关系）。 分句：复句内两个或多个前后有停顿、表达相对完整意义、不带有句末语气和语调、有的前面可添加关联词语的语言单位。 陈述句：用来说明事实的句子。 祈使句：用来要求听话人做某件事情的句子。 疑问句：用来提出问题的句子。 感叹句：用来抒发某种强烈感情的句子。 词语：词和短语（词组）。词，即最小的能独立运用的语言单位。短语，即由两个或两个以上的词按一定的语法规则组成的表达一定意义的语言单位，也叫词组。 二、分类 标点符号分为点号和标号两大类。
点号的作用是点断，主要表示说话时的停顿和语气。点号又分为句末点号和句内点号。 句末点号用在句末，表示句末停顿和句子的语气，包括句号、问号、叹号。 句内点号用在句内，表示句内各种不同性质的停顿，有逗号、顿号、分号、冒号。 标号的作用是标明，主要标示某些成分（主要是词语）的特定性质和作用。包括引号、括号、破折号、省略号、着重号、连接号、间隔号、书名号、专名号、分隔号。 （一）句号 1.用于句子末尾，表示陈述语气。使用句号主要根据语段前后有较大停顿、带有陈述语气和语调，并不取决于句子的长短。 2.有时也可表示较缓和的祈使语气和感叹语气。 请您稍等一下。 我不由地感到，这些普通劳动者也是同样值得尊敬的。 （二）问号 主要表示句子的疑问语气。形式是“？”。 1.用于句子末尾，表示疑问语气（包括反问、设问等疑问类型）。使用问号主要根据语段前后有较大停顿、带有疑问语气和语调，并不取决于句子的长短。 2.选择问句中，通常只在最后一个选项的末尾用问号，各个选项之间一般用逗号隔开。当选项较短且选项之间几乎没有停顿时，选项之间可不用逗号。当选项较多或较长，或有意突出每个选项的独立性时，也可每个选项之后都用问号。 3.问号也有标号的用法，即用于句内，表示存疑或不详。 马致远（1250？―1321）。 使用问号应以句子表示疑问语气为依据，而并不根据句子中包含有疑问词。当含有疑问词的语段充当某种句子成分，而句子并不表示疑问语气时，句末不用问号。
初中英语语法的八种时态的具体用法： 一般现在时表示现阶段经常或习惯发生的动作或存在的状态,或说明主语的特征。 ①一般现在时句子中常有的时间状语：often,usually,sometimes,always,every (day等), once/twice,a (week等), on (Sunday等),never,in the (morning等)。如：They go to the Palace Museum once a year.(他们每年去一次故宫)/ They often discuss business in the evening.(他们经常在晚上商谈生意) ②表示客观真理、事实、人的技能或现在的状态时句子里一般不用时间状语。如：The earth turns round the sun.(地球绕着太阳转)/ Light travels faster than sound.(光传播比声音快) ③表示十分确定会发生(如安排好的事情)或按照时间表进行的事情,用一般现在可以表达将来,句子中可以有将来时间。如：The train for Haikou leaves at 8：00 in the morning.(开往汉口的列车上午8点开车) ④在时间状语从句中(以when, after, before, while, until, as soon as等引导)和条件状语从句中(以if,unless引导),用一般现在时代替一般将来时,句子可以有将来时间。如：Please ring me up as soon as you arrive in Germany.(你一到德国就给我打电话) / If it rains tomorrow,we will have to stay at home.(如果明天下雨我们就只好呆在家) ⑤一般现在时用于倒装句中可以表示正在发生的动作,动词以come, go为主。如：Here comes the bus. (车来了) / There goes the bell.(铃响了)。 ⑥一般现在时常用于体育比赛的解说或寓言故事中。Now the midfield player catches the ball and he keeps it.
闯红灯原因有急事看到没有车看到别人闯 闯红灯人数12 86 369 （2）配合交警在十字路口值勤时，几位同学发现，一些闯红灯的行人不服交警的劝阻和 处罚，甚至出言不逊。针对下面的情况，请你选择一个对象，对其进行规劝。 ①一位大妈不耐烦地说：“等，等，等，一等就是几十秒，我等得起吗？” ②一位大叔掏出一张20元钞票对交警说：“不用找了，我再闯10块钱的。” （3）活动中，赵阳同学写了一篇倡导文明出行的短文。下面是文中的部分内容，请你按 要求帮助他修改。 最近我市发生的几起重大交通事故，原因都是行人不遵守交通法规、闯红灯引发的。我们 应该从中吸取深刻的启示，增强安全意识，[A]严格遵守交通规则，[B]认真学习交通法规，[C] 切实做到文明出行。 ①两处画线句子都有语病，应该将“____”删去，把“____”改为“”。 ②最后三句[A][B][C]语序不合理，应该把[ ]与[ ]调换。（只填序号） 二、阅读（55分） 阅读下面的文字，分别回答问题。 [一] （17分） 西塘古镇 ①西塘，地处太湖东南河道交错的水乡地带。人们依水而居，依靠便利的水上交通从事贸 易活动，明清时期，这里发展成为江南商业重镇。 ②西塘拥有发达的水路交通网，在占地仅1平方千米的古镇内，就有9条河道在此交汇， 将古镇分为8个区块，百余座古桥将古镇连通，因此，古称“九龙捧珠”。 ③西塘的道路交通以桥、廊棚、街弄为主体，在众多古镇中颇具特色。 ④西塘水巷交织，河桥密布，走来走去都是桥。古桥种类繁多，造型也很精美。长长的廊 桥，矮矮的石桥，高高的拱桥，使古镇形成了“人家在水中，水中架小桥，桥上行人走，桥下小 舟过，桥头商铺立，水中倒影游”的水乡美景。 ⑤最有名的环秀桥，建于明万历年间，是古镇中最高的一座桥。拱形的桥身异常优美，桥 东西横跨小桐、北翠两圩。两侧均有桥联，东侧联曰：船从碧玉环中过，人步彩虹带上行。西侧 联曰：往来人度水中天，上下影摇波底月。 ⑥虽然江南古镇大多有廊棚，但西塘的规模最大，临河的街道都有廊棚。所谓廊棚，其实 就是带屋顶的街道。廊棚沿河而建，造型古朴，一色的青瓦盖顶，连为一体，既可遮阳避雨，又 可驻足现景。 ⑦这里有多条街道，其中西街最具特点。西街有水乡极为典型的街道布局，最窄处的宽度 仅供挑担换肩，即一根扁担的长度。临街房屋二楼常常有屋檐延伸，两两相对，形成了“一线天” 的空间布局，构成了别致的古镇风貌。
定语从句用法分析 定语从句在整个句子中担任定语，修饰一个名词或代词，被修饰的名词或代词叫先行词。定语从句通常出现在先行词之后，由关系词（关系代词或关系副词）引出。 eg. The boys who are planting trees on the hill are middle school students 先行词定语从句 #1 关系词： 关系代词：who, whom, whose, that, which, as (句子中缺主要成份:主语、宾语、定语、表语、同位语、补语)， 关系副词：when, where, why （句子中缺次要成份：状语）。 #2 关系代词引导的定语从句 关系代词引导定语从句，代替先行词，并在句中充当主语、宾语、定语等主要成分。 1）who, whom, that 指代人，在从句中作主语、宾语。 eg. Is he the man who/that wants to see you?（who/that在从句中作主语） ^ He is the man who/whom/ that I saw yesterday.（who/whom/that在从句中作宾语） ^ 2）whose 用来指人或物，（只用作定语, 若指物，它还可以同of which互换）。eg. They rushed over to help the man whose car had broken down. Please pass me the book whose cover is green. = the cover of which/of which the cover is green. 3）which, that指代物，在从句中可作主语、宾语。 eg. The package （which / that）you are carrying is about to come unwrapped. ^ （which / that在从句中作宾语,可省略） 关系代词在定语从句中作主语时，从句谓语动词的人称和数要和先行词保持一致。 eg. Is he the man who want s to see you? #3.关系副词引导的定语从句 关系副词when, where, why引导定语从句，代替先行词（时间、地点或理由），并在从句中作状语。 eg. Two years ago, I was taken to the village where I was born. Do you know the day when they arrived? The reason why he refused is that he was too busy. 注意： 1）关系副词常常和"介词+ which"结构互换 eg. There are occasions when （on which）one must yield (屈服). Beijing is the place where（in which）I was born. Is this the reason why （for which）he refused our offer? * 2）在非正式文体中，that代替关系副词或"介词+ which"，放在时间、地点、理由的名词，在口语中that常被省略。 eg. His father died the year （that / when / in which）he was born. He is unlikely to find the place （that / where / in which）he lived forty years ago.
“之”的意义和用法 在古代汉语中，“之”字可作实词，也可作虚词，在不同的语境里有不同的意义和用法，同学们在备考时应引起重视。 一、“之”作实词 1、“之”作动词 这时，“之”的意思是“到……去”“往”“到”“至”。 例1 奚以之九万里而南为?(《逍遥游》) 例2项伯乃夜驰之沛公军。(《鸿门宴》) 例3辍耕之垄上。(《陈涉世家》) 2、“之”作代词 “之”作动词的情况在古代汉语中不多见，作代词相对常见一些。“之”作代词时，一般用作宾语，代人、事、处所，所代的对象大多出现在上下文中。作代词时，“之”又分为指示代词和人称代词。 (1)“之”作人称代词，可译为“他(们)”“她(们)”“它(们)”，用作宾语。 例4君为我呼入，吾得兄事之。(《鸿门宴》)
例5生乎吾前，其闻道也固先乎吾，吾从而师之。(《师说》) 例6虽有(通“又”)槁暴，不复挺者，鞣使之然也。(《劝学》) 例7是何异于刺人而杀之，曰“非我也，兵也”?(《寡人之于国也》) 例8盖将自其变者而观之，则天地曾不能以一瞬。(《赤壁赋》) 从上面所举的几个例子我们可以发现，“之”作人称代词时，一般用在动词之后。 “之”所代的人称在上下文中不一定有具体交代，要根据语言环境进行判断，灵活翻译，如“人非生而知之者”中的“之”，其上下文都找不到先行词，它是泛指“知”的对象，即知识、道理等，可略而不译，也可根据上下文之意译为“知识”或“道理”。 (2)“之”作指示代词，译为“此”“这”“那里”“这样”“这个”等，此时，“之”可作定语，也可作宾语。 例9以故其后名之曰“褒禅”。(《游褒禅山记》) 例10由山以上五六里，有穴窈然，入之甚寒。(《游褒禅山记》) 例11均之二策，宁许以负秦曲。(《廉颇蔺相如列传》) 例12之二虫又何知!(《逍遥游》)