unless 与if ... not 的用法区别
unless 与if ... not 都可表示否定的条件，有时可换用。如：
Come tomorrow unless I phone [if I don’t phone]. 要是我没有打电话，明天就来。
You won’t catch the train unless you hurry [if you don’t hurry]. 你要是不赶快，你就赶不上火车了。
但是在下列情况下，通常要用?if ... not 而不用?unless：
1.当所述条件要引出一种新的想法或情况?(而不是结束已存在的想法或状态?)时。如：
I’ll be angry if I’m not invited to the party. 如果不邀请我参加晚会，我会生气的。?(即“不邀请我去参加晚会?”会导致一种新情况?——“我会生气?”)
I will be surprised if he doesn’t have an accident. 他要是不出事，我倒感到奇怪了。?(即“他不出
事?”会导致一种新情况?——“我感到奇怪?”)
2.当要引出一个表示假想的?(imaginary)条件句时。如：
If he weren’t so silly, he would understand. 他要不是那样傻的话，他就会明白了。?(实际上他很傻?)
If I hadn’t stopped her, she would have jumped down. 要不是我阻止了她，她就跳下去了。?(实际上我阻止了她?)
注：偶尔可见到?unless 用于假想条件句，但有不少语法家反对这一用法，建议学生不要模仿。顺便说一句，?u nless 有时用于引出一个补充前言的话?(此时通常用破折号而不用逗号且不能用?if ... not 替换?)，此时若谈论的是过去的情况，注意不要与表示想象的条件句相混淆。如：
I couldn’t have got to the meeting on time — unless I had caught an earlier train. 我不可能及时赶到会场，除非我赶上了较早的一班火车。?(事实是?“我”没有及时到会?)
若将上句中的?unless 换为?if ... not，则意思有很大差别：
I couldn’t have got to the meeting on time if I had not caught an earlier train. 要是我没有赶上早一班火车，我就不可能及时到会了。?(事实是?“我”及时到会了?)
巧记w h e t h e r与i f 异同
巧记whether与if异同 主从表从同位从，if不用whether用； discuss和介词后，whether引宾从； 不定式、or not后在跟，whether独能显神通； 宾从若是否定句，if发挥其功用； 避免歧义要慎重，其他情况可换用。 一、引导主语从句，常用whether． (1)Whether the meeting will be held is uncertain．会议是否召开还不能确定． (2)It is unknown whether he will come．他是否来还不知道。 3.Whether we’ll go camping depends on the weather. 二、引导表语从句常用whether (1).The question is whether he can finish the work by the end of this week． 问题是到这周末他是否能完成这个工作。 (2).What we want to know is whether he will come to speak to us． 我们想知道的是他能否来给我们讲话。 3.The question is whether it is worth doing. 三、引导同位语从句，常用whether. (1).The question whether he will come is important．他是否来这个问题很重要。 (2).The plan whether we’ll go outing tomorrow hasn’t been made．明天我们是否郊游这个计划还没订。 (3).The question whether we need it has not been decided. 四、引导宾语从句。引导及物动词的宾语从句，用whether, if皆可； 介词的宾语从句，一般只用whether引导；
If，unless 一结构 If 作“如果”解，用来引导条件状语从句，可放在主语前面或后面。二时态 1 当谈论未来可能出现的情况时,主句用一般将来时,if从句用一般现在时。 例：If I am free, I will come to see you . 2 当谈论可预测的、反复出现的情况时，主句和if 句都用一般现在时，此时if 相当于when. 这类句子通常表示不受时间限制的自然法则表普通真理和客观事实 例：If you cool the water below zero, it turns into ice. 三转换 If 从句和主句还可以由“祈使句+and/or+简单句代替”，and 表示句意顺承；or则意为“否则”。 If you study hard, you will pass the exam. = Study hard, and you’ll pass the exam. If you don’t hurry up, you’ll miss the train. = Hurry up, or you’ll miss the train. 另外，unless 也可以引导条件状语从句，相当于if…not,“如果不、除非”。 I will plant the flowers if it doesn’t rain tomorrow. = I will plant the flowers unless it rains tomorrow. Unless: conj. 除非, 如果不 Unless you take more care, you’ll have an accid ent. 如果不多加小心的话，你会出事故的。 更详细的如下 一、unless的基本用法 unless“除非……如果不……”引导否定意义的真实条件句有时也可引导非真实条件句 (1)主句为肯定句。 Unless I visit every bookstore in town．I shall not know whether I can get what want． 如果我不到城里每一家书店去看看，我就不知道是否能买到我想要的书。 You will miss the bus unless you hurry up．你要不快点就会错过班车。 (2)主句为否定句。 I wouldn't be saying this unless I were sure of the facts． 要是我对这些事情没有把握，我就不说这话了。 二、应注意的一些问题 1．unless不能与if'"not换用的情况 unless在意义上相当于if...not，因此在有些场合中unless与if...not可互换使用。
whether和if的用法区别 whether与if作“是否”讲，在用法上有相同之处，也有不同之处。 一、相同之处。 和if都能引导宾语从句，常置于see,ask,learn,tell,wonder,doubt,find out等动词之后。 如：He asked me whether/is I could help him. I want to know whether/if he lives there. 和if都可用it作形式主语从句中。如：it's uncertain whether/if he'll come this evening. 3.在be uncertain/doubtful之后，常用whether引导宾语从句，有时也可以用if，如：We are uncertain whether/if Mary will come. 二、不同之处。 可置于句首引导主语从句，而if不能。如：___the 2000 Olympic Games will be in Beijing is not known yet. 答案是C。 可用在介词之后，引导宾语从句，而If则不能。如：Success depends on whether we make evough effort. 可引导表语从句，if则不能。如：The puestion is whether it is not worth doing. 4.在名词之后引导同位语从句时，用whether而不用if。如：The question whether the students answered correctly should be decided by the teacher. 后可接不定式，而if不能。如：Please tell us whether to go or stay here. 6.在有些动词（如discuss）之后，只能用whether，而不用if引导宾语从句。如：We discussed whether we should close the shop. 7.在引导否定概念in宾语从句时，只能用if，而不用whether.如：he asked me if I hadn't finished my work. 英语时态一般现在时表示现在、经常或习惯的动作或状态和普遍现象、常识或客观真理；一般过去时用于过去某一时间内发生的或过去习惯性的动作或状态；一般将来时表示将要发生的动作或存在的状态，将来打算做的事情；现在完成时表示过去发生的动作造成目前的结果和对现在造成的影响或表示从过去延续至今的动作、状态和习惯等；将来完成时表示将来某时之前业已完成或发生的事情；过去完成时表示过去某时间之前已经发生的动作或状况，即过去的过去。注意每一种时态与其他时态的交叉使用情况。英语共有十六种时态，其表现形式如下(以study为例)： 一般时进行时完成时完成进行时 study studies am studying is studying are studying have studied has studied have been studying has been studying studied was studying were studying had studied had been studying shall study will study shall be studying will be studying shall have studied shall have been studying will have been studying should study would study should be studying would be studying should have studied would have studied should have been studying would have been studying 但考试中出现的一般有以下几种。 第一节一般现在时 一、表示一般性或经常发生的动作或状态 二、表示习惯性动作和状态或普遍的现象或常识 三、表示客观事实、客观规律和客观真理。在宾语从句中，即使主句的谓语动词用了过去时，只要从句表示的是客观真理，从句的谓语动词也要用一般现在时 四、祈使句必须用动词原形，其否定结构用“don`t＋动词原形”，如：Go and fetch some water. ／Don`t do that. 五、在反义疑问句中，如果主句用肯定句，那么，反问句用否定形式；如果主句用否定形式，那么，反问句就用肯定形式。而且前后在时态上要一致。但祈使疑问句用won`t you进行反问。如：See a film tonight, won`t you？ 注：①祈使句后边可用附加疑问句，以加强语气。如果祈使句用肯定形式，附加疑问句用否定形式；如果祈使句用否定形式，附加句用肯定形式；如：Come here next Sunday, won`t you ／Don`t tell it to anyone, will you ②但如果祈使句的前一句有了表示强烈肯定的语言环境，即使祈使句用了肯定形式，其附加成分也可以用“will you”(表示肯定，如
If引导条件状语从句的详细用法解答 引导条件状语从句最常用的连词是if，常见的if条件状语从句表示在某条件下，某事很可能发生，条件是可能存在的，主句中某种情况发生的概率也是很高的。如： If you ask him，he will help you．如果你请他帮忙，他会帮你的。 If you fail in the exam，you will let him down．如果你考试不及格，你会让他失望的。 If you have finished the homework，you can go home．如果你作业做完了就可以回家了。 另外，if从句还表示不可实现的条件或根本不可能存在的条件，也就是一种虚拟的条件或假设。从句多用一般过去时或过去完成时，表示对现在或过去的一种假设。如： If I were you，I would invite him to the party．如果我是你，我会邀请他参加聚会。 I would have arrived much earlier if I had not been caught in the traffic．要不是交通堵塞，我本会来得早一些。 另外你还要注意if 条件句的时态搭配 1．if从句用一般现在时，主句用一般将来时 If he runs he’ll get there in time. 如果他用跑的，他就会及时赶到那儿。 The cat will scratch you if you pull her tail. 如果你拉猫的尾巴，它就会抓你。2．if从句用一般现在时，主句用may/might/can If the fog gets thicker the plane may/might be diverted. 如果雾在大一些，飞机可能就会改在别的机场降落。 If it stops snowing we can go out. 如果雪停了，我们就可以出去。 3．if从句用一般现在时，主句用must/should If you want to lose weight you must/should eat less bread. 如果你想减肥，你必须少吃面包。 4．if从句用一般现在时，主句用一般现在时 If you heat ice it turns to water. (也可用will turn)如果把冰加热，它就会化成水。5．if从句用现在进行时，主句用一般将来时 If you are looking for Peter you’ll find him upstairs. 如果你是在找彼得，上楼就会找到他。 6．if从句用现在完成时，主句用一般将来时 If you have finished dinner I’ll ask the waiter for the bill. 如果你吃完了，我就叫服务生来算账 注意： 学习" if " 引导的条件状语从句的用法,现在总结一下: if 条件句不一般,几个要点记心间; 条件句,放在前,逗号要放句中间。 条件句表可能，主句多用将来时； 条件句表事实，主句常用现在时。
Unless 与 if not 1. unless 与if … not 都可以用来引导条件状语从句， unless 的语气较重，从句中的动词用一般现在时代替一般将来时。例如： We will visit the Great Wall tomorrow unless it rains. 除非明天下雨，否则我们就去参观长城。 I won't believe what you said unless I've seen it with my own eyes. 我要亲眼所见才能相信你所说的。 Don't enter the lab unless you are permitted to. 只有经过允许才能进入实验室。 2. 有的同学在遇到使用 unless 的句子时，弄不清该用肯定还是否定而出错。这时最好的办法是将 unless 替换成if … not 的结构，从而就一目了然了。例如： I won't go to the party unless I am invited. （ =I won't go to the party if I am not invited. ） 如果没有人邀请我，我是不会去参加聚会的。 3. 由于 unless 与if … not 的语气不同，有时两者替换后，其意思就不一样了。例如： Unless he were my friend, I shouldn't expect his help. 除非他是我的朋友，我才会期待他的帮助。（本句的潜在意思为：他并不是我的朋友。） If he were not my friend, I shouldn't expect his help. 如果他不是我的朋友，我就不会期待他的帮助了。（本句的潜在意思为：正因为他是我的朋友，我才会期待他的帮助。） 4. 在平时使用过程中，要注意 unless 与 until 的区别。
初中英语――条件状语从句 一．if 引导的条件状语从句 引导条件状语从句最常用的连词是if，常见的if条件状语从句表示在某条件下，某事很可能发生，条件是可能存在的，主句中某种情况发生的概率也是很高的。如： If you ask him，he will help you．如果你请他帮忙，他会帮你的。 If you fail in the exam，you will let him down．如果你考试不及格，你会让他失望的。 If you have finished the homework，you can go home．如果你作业做完了就可以回家了。 另外，if从句还表示不可实现的条件或根本不可能存在的条件，也就是一种虚拟的条件或假设。从句多用一般过去时或过去完成时，表示对现在或过去的一种假设。如： If I were you，I would invite him to the party．如果我是你，我会邀请他参加聚会。 I would have arrived much earlier if I had not been caught in the traffic．要不是交通堵塞，我本会来得早一些。 另外你还要注意if 条件句的时态搭配 1．if从句用一般现在时，主句用一般将来时 If he runs, he’ll get there in time. 如果他用跑的，他就会及时赶到那儿。 The cat will scratch you if you pull her tail. 如果你拉猫的尾巴，它就会抓你。 2．if从句用一般现在时，主句用may/might/can If the fog gets thicker, the plane may/might be diverted. 如果雾在大一些，飞机可能就会改在别的机场降落。 If it stops snowing, we can go out. 如果雪停了，我们就可以出去。 3．if从句用一般现在时，主句用must/should If you want to lose weight, you must/should eat less bread. 如果你想减肥，你必须少吃面包。4．if从句用一般现在时，主句用一般现在时 If you heat ice, it turns to water. (也可用will turn)如果把冰加热，它就会化成水。 5．if从句用现在进行时，主句用一般将来时 If you are looking for Peter, you’ll find him upstairs. 如果你是在找彼得，上楼就会找到他。6．if从句用现在完成时，主句用一般将来时 If you have finished dinner, I’ll ask the waiter for the bill. 如果你吃完了，我就叫服务生来算账注意： 学习" if " 引导的条件状语从句的用法,现在总结一下: if 条件句不一般,几个要点记心间; 条件句,放在前,逗号要放句中间。 条件句表可能，主句多用将来时； 条件句表事实，主句常用现在时。 在if 引导的条件状语从句中，如果从句谈论的是一个有可能发生的事实及其产生的相关的结果，主句用一般将来时态，从句用一般现在时态。如： We can walk there if we can't find a bus. If it rains tomorrow, we will not go to the zoo. What will you do if you find a panda in danger? 如果if 条件句谈论的是重复发生和预示要发生的情景和事件，则主从句大多用一般现在时态。如： If bears are in danger, they attack people. 在if 引导的条件状语从句中，if 和条件句位置灵活，可直接放在主句后面，若if 条件句放句首，从句后面要加逗号，和主句隔开。还要注意前后时态一致原则
STRUCTURE 结构 As mentioned above, unless is a conjunction which we use in conditional phrases. In written English, the clause that follows unless is the subordinate clause (SC) meaning that it needs a main clause (MC) to make a complete sentence. It is similar to how we use if in conditional phrases. 之前提过，unless是在条件句中使用的连词。在书面语种，使用unless的从句叫做从属句(SC)，需要主句(MC)让句子完整。这就像if在条件句里的用法一样。 When unless comes before a main clause we use a comma: unless放在主句之前加逗号： Unless it rains, we’ll go for a picnic tomorrow. [en](SC) (MC) [/en] 除非下雨，否则我们明天去野餐。 When the main clause comes first, no comma is required: 主句在前，不需要逗号： They won’t come unless you invite them.
[en](MC) (SC) [/en] 除非你邀请他们，否则他们不会来。 Unless is like If in that we don’t not use will/would after it. We only use the present simple tense. 像if一样，我们不会在unless后面使用will/would。只使用一般现在时。 Unless I hear from you, I’ll see you at 5pm. 除非你通知我，否则我和你下午5点碰面。 HOW DO WE USE “UNLESS”? 如何使用“unless”? Unless and if not unless和if not Ok, so unless is similar to “if …..not” and together they mean “except if”. Note: We refer to real conditional situations and NOT impossible situations. unless和if…not很相似，它们都表示“除非”。注意：我们指的是真实的条件情况，而不是不可能的情况。
If和whether if不能替换whether的5种情况 1.正式文体中，句中有or not 时 2.引起主语，表语，同位语从句时 3.作介词宾语时 4.放不定式前，与不定式组成词组时 5.作discuss等词的宾语时 以上是if和whether表示"是否"之意的区别，此外，if还有加入的意思，引起条件状语从句；而whether 另有不管无论之意，引起让步状语从句 whether与if作“是否”讲，在用法上有相同之处，也有不同之处。 一、相同之处。 1.whether和if都能引导宾语从句，常置于see,ask,learn,tell,wonder,doubt,find out等动词之后。 如：He asked me whether/is I could help him. I want to know whether/if he lives there. 2.whether和if都可用it作形式主语从句中。如：it's uncertain whether/if he'll come this evening. 3.在be uncertain/doubtful之后，常用whether引导宾语从句，有时也可以用if，如：We are uncertain whether/if Mary will come. 二、不同之处。 1.whether可置于句首引导主语从句，而if不能。如：___the 2000 Olympic Games will be in Beijing is not known yet. A.whether B.If C.Whether D.That 答案是C。 2.whether可用在介词之后，引导宾语从句，而If则不能。如：Success depends on whether we make evough effort. 3.whether可引导表语从句，if则不能。如：The puestion is whether it is not worthdoing. 4.在名词之后引导同位语从句时，用whether而不用if。如：The puestion whether the students answered correctly should be decided by the teacher. 5.whether后可接不定式，而if不能。如：Please tell us whether to go or stay here. 6.在有些动词（如discuss）之后，只能用whether，而不用if引导宾语从句。如：We discussed whether we should close the shop. 7.在引导否定概念in宾语从句时，只能用if，而不用whether.如：he asked me if I hadn't finished my work. whether和if都可以引导宾语从句，表示“是否”，在口语或间接引语中两者可以互换使用。如： I wonder if / whether I can get some advice from you. Ask him whether / if he can come. 但在有些情况下，whether和if的用法有一定区别。 1. whether引导的从句常可以与连词or或or not直接连用，而if一般不能。如： 正：Let me know whether you can come or not. 误：Let me know if you can come or not. 2. 当宾语从句提到句首时，只能用whether引导，而不能用if。如： 正：Whether it is true or not, I can’t tell. 误：If it is true or not, I can’t tell. 3. whether可以引导带to的不定式，if则不能。如： 正：I don’t know whether to accept or refuse.
C h a p t e r1语法If 和unless引导的条件状语从句 我们用if引导的条件状语从句来讨论可能的条件以及该条件成立时可能的结果。一. 学习if引导的条件状语从句的用法，我们可先从如下的口诀入手： If条件句不一般，几个要点记心间； 条件句，放在前，逗号要句中间 条件句表可能，主句多用将来时； 条件句表事实，主句常用现在时。 We can walk there if we can’t find a bus. 如果我们找不到公车，也能走路去那里 主句条件状语从句 If it rains tomorrow, we will not go to the zoo. 如果明天下雨，我们就不去动物园 条件状语从句主句 What will you go if you find someone in danger? 主句条件状语从句 如果你发现某人有危险，你会怎么做？ If 条件句有不同的类型，简述如下： 1. 用if条件句表达客观真理或普通现象 If条件句用于表达客观真理或普通现象时，主，从句时态均用一般现在时，如：Eg. If you freeze water, it turns into ice. A fish dies if you take it out of water. 2. 用if 条件句表示将来可能发生的事情 在表示将来可能发生的事情的if条件句中，主句用一般将来时，而if从句用一般现在时表示将来的时间，即主将从现
Eg. If I like the house, I will buy it. 如果我喜欢这房子，我就会把它买下 I will tell her if I see her. 如果我见到她，我就会告诉她。 主句中的will也可以用情态动词can, may 或might等代替。如： Eg. If they are friendly，I might invite them to the party. 如果他们很友善，我可能会请他们去参加聚会 If we hurry now, we can stop for coffee later. 如果我们现在抓紧时间，就可以稍后去喝咖啡注意：在条件句中，主句部分只能使用动词will的一般将来时，不能使用be going to的结构 二. Unless 的条件句 表示在特定条件下，才决定做或不做一件事，中文用的连接词一般是“除非”和“否则”。如：除非刮台风，否则演唱会将如期进行。在英语中，我们可以用unless表达这个意思，相当于if not。以这个句子为例： The concert will be held as schedule unless there is a typhoon. = the concert will be held as schedule if there is not a typhoon She will keep on singing unless she is told to stop. 她会一直唱下去，除非有人叫她停止 = she will keep on singing if she is not told to stop 也可以用or(否则) 来做同义句转换 Unless you listen carefully, you won’t know the answer. = if you don’t listen carefully, you won’t know the answer. = you should listen carefully, or you won’t know the answer. 深圳中考题： 1. If I ________ his phone number, I will tell you. A.find B. found C. will find D. have found 2. We will go camping if it _______ tomorrow.
1）(肯定)表示“除……之外(还)……” besides 和in addition to 同义 She knows Japanese besides English. In addition to English, she knows Japanese. 2）(否定)当与nothing，nobody或no one等否定意义的不定代词连用时，表示“除…之外(其余都不)”。besides与except同义， except 表示“除……外，(其余都)……”，常与“all，every，no，none，n othing”等含有整体肯定或否定意义的词连用。 All of them went to climb the mountain except me. 3）except for：它的宾语与前述对象完全是两回事。 The room was very cold and, except for Jack, entirely empty完全是空荡荡的. 4）except：指同一类事物的总体中除去一部分。 He gets up early everyday except Sunday. 5) except that 后面跟从句，语意与上同。 He has always been in good health except that he has had a slight headache in the past few days. 6）but：常可与except互换，强调“不在其中”。 Everyone attended the meeting but Mary. 7）besides:强调“除此之外，还包括”。 She can speak French and Japanese besides English. 8）apart from；其含义主要依据上下文而定，有时可与except换用，有时可代替besides. Apart from the price, the hat doesn't suit me. 9）except 用于同类之间。 other than：固定用法，用于否定句中。意思是除了……，除……之外。与excep/but 相同，都是表示从总体中除去一部分，后接名次、代词或不定式。 except for 用于不同类的。除此之外，什么都在 apart from 在同类或不同类都能用 10）except for和apart from接名词, 但apart from是从"什么分离出来"的意思 而except for是"除了"的意思 11) unless conj. 除非，如果不 . unless用于引出某事发生或成立所必需的条件
if与whether用法区别 收集整理：王俊尧 1.下列情况只能用whether： （1）直接与or not连用时,往往用whether(if…or not也可以使用)。如: Let me know whether or not he will come. (= Let me know whether / if he will come or not.) 让我知道他是否能来。 I don't know whether or not he does any washing. (= I don't know whether / if he does any washing or not.) 我不知道他在家洗不洗衣服。 I wonder whether we stay or whether we go. 我想知道我们是去还是留。 (2) 在介词之后用whether。如： I'm interested in whether he likes English． 我关心的是他是否喜欢英语。 We're thinking about whether we can finish the work on time． 我们正在考虑是否能按时完成这项工作。 I worry about whether I hurt her feelings． 我担心是否伤了她的感情。 (３)在不定式前用whether。如： He hasn't decided whether to visit the old man． 他尚未决定是否拜访那位老人。 I don't know whether to go．我不知去否。 He hasn't decided whether to go by bus or by train． 他还未决定是乘公共汽车去还是坐火车去。 （４）whether置于句首时，不能换用if。如： Whether this is true or not，I can't say． 这是否真的我说不上来。 （５）引导主语从句和表语从句时宜用whether。如： Whether she will come or not is still a question． 她是否能来还是个问题。 The question is whether we can catch the bus． 问题是我们能否赶上公共汽车。 （６）若用if会引起歧义时，则用whether。如：
1.whether和if均可用来引导主语从句，但if引导的从句不能位于句首。 如：Whether they win or lose is all the same to me. 他们是赢是输於我都一样.（此时whether不能换作if ） It's doubtful whether there'll be any seats left.说不上还有没有空座位了.(此句whether能换作if) 2.whether和if均可用来引导宾语从句。如： ①I don't know whether/if I will be able to come.我不知道我是否能来. ②She asked me whether/if I was interested in working for her.她问我是否有兴趣为她工作。 ③We'll be told tomorrow whether we should take the exam or not.我们明天才知道是不是应该参加考试. ④I asked him whether he had done all the work himself or whether he had had any assistance. 我问他这些工作都是他自己做的还是别人帮他做的. ( 注意: 在两个供选择的从句之间若用or字, 则须重复whether一字. ) 注:⑴当强调宾语从句并将其提前时只能用whether。 如:Whether I'll have time to go with you I am not sure.我很难说我们是否有时间跟你们一起去。 ⑵从句作介词宾语时只用whether不用if。 如:She was undecided about whether she should accept his offer. 她拿不定主意应该不应该接受他的好意 ⑶当whether和or not连用时，只用whether不用if。当or not放在whether引导的从句句尾，则可以用if来替换。 如: I don’t know whether or not he will come.我不知道他是不是回来。 I'll be happy whether/if I get the job or not我能不能得到那份工作都一样高兴 ⑷当whether和or 连用表示明确的选择时，只用whether不用if。 如:He asked me whether I wanted to go there by train or by bus. 他问我是想乘火车还是坐公共汽车去那里。 He hesitated about whether he should drive or take the train.他开车去还是坐火车去, 犹豫不决注:whether 和or 连用还可以引导让步状语从句,此时也不用if。 如：We'll go on with the work, whether we can find the necessary tools or not. 不管我们能否找到所需的工具,我们要把这件工作做下去。 Whether or not it rains / Whether it rains or not, we're playing football on Saturday. 无论下不下雨, 我们星期六一定踢足球. ⑸动词discuss，decide,consider等后习惯上也常用Whether引导从句，不用if。 They discussed whether they should leave at once.他们讨论了是否应该马上离开。We discussed whether the house should be sold. 我们讨论了这房子是否应卖掉。 3.表语从句用whether引导不用if. 如:①The doubt was whether you had broken the beautiful vase. 疑问是你是否打坏了这只漂亮的花瓶。 4.同位语从句用whether引导不用if. 如:①The question whether we'll build another lecture building hasn't been settled. 是否要另建一幢教学楼的问题还未决定。 5. 在动词不定式之前，只能用whether，不能用if。 如:①The question is whether to go to Munich or Vienna. 问题是去慕尼黑还是去维也纳. ②She doesn't knows whether to get married now or wait. 是否现在结婚或是等待她不知道。 ③We were wondering whether to go today or tomorrow. 我们弄不清是今天走还是明天走. ④I'm not sure whether to resign or stay on. 我拿不准主意是辞职还是留任. Answers: BADDC ABCAB ABADD B
If, unless 专项练习 一、完成下列句子 1. I’m sure if he _____(go) to the party, he________ (have) a great time. 2. If the rain _______(stop) tonight, we will go to the cinema. 3. I’ll buy a computer if I ______(have) enough money. 4. You _________(not get) nervous if you _____(do ) enough exercise. 5. I want to know if he _________(come) tomorrow, if he _______(come), I __________(give) the massage to him. 6. Comrade Wang didn't know if there _______ (be) on English evening that day. 7. Please tell me if she _______ (come) again next time. 8. Mike asked me if we _______(ask) any questions the next class. 9．The twins ______________ (fight) if they_______________ (argue). 10. I ____________ (have) a bake sale if I _____________ (need) money for education. 二、选择 ( )1. I don’t know _____ he will come tomorrow. _____ he comes, I’ll tell you. A. if; Whether B. whether; Whether C. if; That D. if; if ( ) 2. He said he would help me with my maths if he _______ free. A．was B．will be C．would be D．is ( ) 3. Tommy, do you know if Frank ________ to the zoo this Sunday if it ________? -Sorry, I have no idea. A. will go; is fine B. goes; is fine C. will go; is going to be fine D. goes; will be fine ( ) 4. -Listen! It is still noisy in the head teacher’s office. -Go and see ________ they have finished correcting the papers yet. A. though B. whether C. unless D. while ( ) 5. He asked me ________ we could go to Beijing to watch the game by plane. A. that B. if C. how D. what （）6 . The volleyball match will be put off if it ______. A. will rain B. rains C. rained D. is raining （）7. Difficulties are nothing if we ______ not afraid of them A. will B. shall C. are D. do （）8. I don’t like to be interrupted if I______. A. speak B. will speak C. am speaking D. spoke （）9. If you______ the book you will understand the story better. A. will be reading B. have read C. will have read D. read ( ) 10. There is going to______ a sports meeting next week. If it ______ , we’ll have to cancel it.. A. be; will rain B. have; will rain C. be; rains D. give; is going to rain （）11. If you ______ a chance to study in a foreign country, just take it. A. getting B. had got C. will get D. get ( ) 12. I want to know if they ____ the spring sports meeting next month. If they ____ it, I must get ready for it. A. hold; will hold B. will hold; hold C. hold; hold D. will hold; will hold （）13. –Look, what have you done? -Sorry. I think if I ________ another chance, I’ll do it better. A. give B. will be given C. will give D. am given （）14.If you _______ him tomorrow, please ask him if he ______ to work on the farm with us. A. see ; goes B. will see; goes C. will see; will go D. see; will go ( ) 15. It makes no difference __________. A. whether will you come tomorrow. B. Whether or not will be pass the exam C. If he will come to the meeting or not D. Whether he will come to the meeting or not ( ) 16. Even now many people still remembered ________ when hey heard about the 1976 earthquake in Tangshan. A. what were they doing B.that they were doing C. what they were doing D.if they were doing ( ) 17. In summer, food goes bad easily _____ it is put in the refrigerator. A. until B. if C. unless D. since ( ) 18. –I hear Jack Chan will come to Shanghai next week. -Really? _______ he comes, my younger sister will be very happy. A. If B. Until C. Unless D. Before ( ) 19. We will have no water to drink______ we don’t protect the earth. A．until B. before C. though D. if ( ) 20 –May I surf the Internet now? - No, _______ you have finished doing the dishes.