if和unless部是最常用的条件从句连接词。unless在意义上等于“if...not”，并且
语气较强。if 可用于引导虚拟条件句，unless一般不能引导虚拟条件句。unless在意义
上相当于if...not...，因此在有些场合if...not...可为unless所代替。
unless和if的具体区别
1. 当所述条件会结束已经存在的想法，状态或趋向时，两者都可以。
例如：We shall go unless it rains tomorrow. =We shall go if it doesn’t rain tomorrow.
如果明天不下雨，我们就去。（“下雨” 会结束“去” 这一已经存在的趋向）
You will be late unless you take taxi. =You’ll be late if you don’t take taxi.
如果不打的你就要迟到。“打的”（会结束“迟到” 这一趋向）
2. 当所述条件会导致一种新的想法或状况时，通常用if not。
例如：I’ll be late if you not let me go now.
你如果不让我现在走我会迟到的。（“不让现在走”就会导致“迟到”这种新情况）
3. 表示虚拟条件，既与实际事实相反的状况时，只能用if not。
例如： She would be angry if you had not invited her to party.
你要是没邀请她，她肯定生气。
4. 和否定表达连用时，只能用unless。
例如： I will go unless nobody invite me.
除非没人邀请我，否则我肯定会去。
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
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。
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.
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
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.
If 和whether的区别 if和whether都可译为\"是否\",二者引导宾语从句时通常可以互相替换,口语中多用if 代替whether.例如：Ask if/whether he plans to come to the meeting. 而以下几种情况中, 只能用whether: 1. 强调两方面的选择,特别是句中有or not时.如： Let me know whether you can come or not. 2. 宾语从句前置时.如： Whether this is true, I can\'t say. 3. 引导主语、表语、同位语从句时.如： Whether the football game will be played depends on the weather. （主语从句） The question is whether he can do it. （表语从句） The question whether we should go with them must be decided at once. （同位语从句） 4. 在介词之后作介词的宾语时.如： I haven\'t settled the question of whether I\'ll go back home. 5. 在不定式前与不定式一起组成词组时.如： Whether to go or stay is still a question. 6. 在discuss, decide 等动词后作宾语时.如： We discussed whether we should go there by plane. 值得注意的是：if还可以引导条件状语从句,是\"假如；如果\"之意,而whether可以引导让步状语从句,是\"不管；无论\" 之意.如： If you ask him, he will help you. I shall go, whether you come with me or stay at home. 一、if或whether引导宾语从句时,作“是否”讲,常放在动词ask 、see 、say 、know 和find out等后面.一般情况下,两者常可换用,在口语中多用if.如： 例1 Nobody knows whether (if) it will rain tomorrow. 没有人知道明天是否下雨. 例2 Lucy asked whether (if) they had a cotton sweater .露西问他们是否有棉制的羊毛衣. 二、if或whether引导宾语从句时,要注意三个方面,即连词、语序和时态. 1 if或whether不能和that 或其它连词（副词）同时使用,也不能省去.如： 例3 我不知道他今天是否会来. [误] I don’t know that if(whether) he will come here today . [正] I don’t know if(whether) he will come here today . 例4他走过来看看猫是否出了毛病. 误] He came to see what if (whether) there was wrong with his cat . [正] He came to see if (whether) there was wrong with his cat . 2 if或whether引导的宾语从句时,虽具有疑问意义,但从句语序应用陈述句语序.如：例5 Did you know the way to the hospital ? The old woman asked me . The old woman asked me .if (whether) I knew the way to the hospital .老妇人问我是否知道去医院的路. 3 if或whether引导的宾语从句应和主句的时态保持一致.即主句为一般现在时,从句用
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.
unless的用法 unless是从属连词，引导条件状语从句，含有否定意义，相当于if条件状语从句的否定形式。所以unless = if not。注意：unless引导的条件状语从句和if条件状语从句，与其它时间状语从句一样，用一般现在时代替将来时。 Unless: conj. 除非, 如果不 Unless you take more care, you’ll have an accident. 如果不多加小心的话，你会出事故的。 My baby sister never cries unless she is hungry. 我那刚出生的妹妹除非饿了，否则她是从来不哭的。 Don’t promise anything unless you’re 100 per cent sure. 不要作任何的许诺, 除非你有百分百的把握。 Unless bad weather stops me, I run every day. 除非坏天气作梗，每天我都跑步。 木头容易燃烧，除非是水湿了。 We'll be late unless we speed up. 我们要不加快些，就会迟到了。 You'll fail in English unless you work hard. 除非你努力学习，否则你英语将不及格。 You'll miss the bus unless you walk more quickly. 除非你走快一点，否则将赶不上公共汽车。 You won't hear anything unless you roll the tape ahead. 除非你把录音带往前转，否则你是不会听到任何东西的 You will never pass the exam unless you study harder. 除非你加紧学习，否则考试永远过不了关。 更详细的如下 一、unless的基本用法 连词unless意为“除非……如果不……”，“除了……”，多引导一个否定意义的真实条件句，有时也可引导非真实条件旬。unless引导条件句时，主要用于下列情况。 (1)主句为肯定句。如： Unless I visit every bookstore in town．I shall not know whether I can get what l 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。 You’ll fail in chemistry again unless you work harder．如果你不再加把劲，你化学考试还会不及格。 (2)主句为否定句。如： Unless you oil the motor regularly．it won’t run smoothly．要不是你经常给发动机上油。它就不会转得那么顺畅。 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。 You will never get anywhere unless you have set your goal．如果你不设定目标，你哪儿也去不了。 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。
I f和w h e t h e r的区别 if 和 whether都可译为\"是否\",二者引导宾语从句时通常可以互相替换代替 whether.例如：Ask if/whether he plans to come to the meeting. 几种情况中 , 只能用 whether:,口语中多用 if 而以下 1.强调两方面的选择 ,特别是句中有 or not 时.如： 2.宾语从句前置时 .如： 3.引导主语、表语、同位语从句时 .如： Whether the football game will be played depends on the weather.（主语从句） The question is whether he can do it.（表语从句） The question whether we should go with them must be decided at once.（同位语从句） 4.在介词之后作介词的宾语时 .如： 5.在不定式前与不定式一起组成词组时 . 如： Whether to go or stay is still a question. 6. 在 discuss, decide等动词后作宾语时 .如： We discussed whether we should go there by plane. 值得注意的是：if 还可以引导条件状语从句 ,是\" 假如；如果 \" 之意 ,而 whether 可以 引导让步状语从句 ,是 \" 不管；无论 \" 之意 .如： If you ask him, he will help you. I shall go, whether you come with me or stay at home. 一、if 或 whether引导宾语从句时 ,作“是否”讲 , 常放在动词 ask 、see 、say 、know 和 find out 等后面 . 一般情况下 ,两者常可换用 , 在口语中多用 if. 如： 例 1 Nobody knows whether (if) it will rain tomorrow.没有人知道明天是否下雨. 例 2 Lucy asked whether (if) they had a cotton sweater .露西问他们是否有棉制的羊毛衣 . 二、 if 或 whether引导宾语从句时 ,要注意三个方面 ,即连词、语序和时态 . 1 if或 whether不能和 that 或其它连词（副词）同时使用,也不能省去 . 如： 例 3我不知道他今天是否会来 . [ 误 ] I don ’ t know that if(whether) he will come here today . [ 正 ] I don ’ t know if(whether) he will come here today . 例 4他走过来看看猫是否出了毛病 . 误] He came to see what if (whether) there was wrong with his cat . [ 正 ] He came to see if (whether) there was wrong with his cat . 2 if 或 whether引导的宾语从句时,虽具有疑问意义,但从句语序应用陈述句语序. 如：例5 Did you know the way to the hospital ? The old woman asked me . The old woman asked me .if (whether) I knew the way to the hospital .老妇人问我是否知道去医院的路. 3 if 或 whether引导的宾语从句应和主句的时态保持一致. 即主句为一般现在时,从句用
Chapter 1 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