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1、if 的用法1 一、一、if 作为连词，引导作为连词，引导条件状语从句条件状语从句，它表示，它表示的意思是的意思是“假如假如”“如果如果”等。在复合句中如果主等。在复合句中如果主句用将来时，则句用将来时，则if引导的状语引导的状语1. If it doesnt rain, we will go to the park next Sunday.二、二、if还可以引导还可以引导让步状语从句让步状语从句。这时。这时if当作当作“即使是即使是”，“虽说虽说”解解1. If shes poor，at least shes honest 虽说她很穷，但至少她还是诚实的。虽说她很穷，但至少她还是诚实的。2.
2、 If I am wrong，you are wrong， too 即使说即使说我错了，那么你也不对。我错了，那么你也不对。从句用一般现在时从句用一般现在时2三、三、if作为连词还可以引导作为连词还可以引导宾语从句宾语从句。引导宾语引导宾语 从句时和从句时和whether意思相同。意思相同。1. Lily asked if whether she liked it. 莉莉问她是否喜欢它。莉莉问她是否喜欢它。四、四、if引导引导时间状语从句时间状语从句，当，当if做做“当当”或或“无论何时无论何时”解而不含有条件之义时，解而不含有条件之义时，if从句中从句中的时态与主句中的时态的时态与主句中的时
3、态相同相同。1. If you mix yellow and blue，you get green你将黄色与蓝色混合，便会得到绿色。你将黄色与蓝色混合，便会得到绿色。2. If she wants the servant，she rings the bell.每当她需要仆人时，她便按铃。每当她需要仆人时，她便按铃。3五、五、if后接后接否定否定动词，用于感叹句中，表示动词，用于感叹句中，表示沮丧沮丧、惊奇惊奇等。等。 I. Well，if I havent left my false teeth at home! 真倒霉，我把假牙丢在家里了真倒霉，我把假牙丢在家里了! 2. And if he
4、 didnt try to knock me down!(What do you think he did! He tried knock me down!)六、六、用于用于虚拟语气虚拟语气中，中，if从句中用从句中用过去式过去式，表示不，表示不可能实现，大概不会实现或提出作为考虑的假定可能实现，大概不会实现或提出作为考虑的假定条件条件1. If you were a bird, you could fly.假使你假使你是只鸟，你便会飞了。是只鸟，你便会飞了。你猜他想做什么你猜他想做什么?他想把我撞倒他想把我撞倒!4另外另外，if从句中用从句中用过去完成式过去完成式，表示过去未实现的，表示过去
5、未实现的条件条件(例如由于不可能实现或某人之未能实行例如由于不可能实现或某人之未能实行)。 1. If they had started earlier，they would have arrived in time要是他们早些动身，他们便可及时到达了。要是他们早些动身，他们便可及时到达了。 第三，在第三，在文学体裁文学体裁中，中，if有时可省略，然后将主语有时可省略，然后将主语与所用的限定动词与所用的限定动词(尤其是尤其是were，had，should)倒倒置置。1. Should it (=if it should)be necessary，I will go. 倘若有必要，我会去的。倘若
6、有必要，我会去的。2. Were I(=if I were) in your place，I would do the same. 如果我处于你的位置，我也会这样干的。如果我处于你的位置，我也会这样干的。5七、七、if与其它一些介词的连用。与其它一些介词的连用。首先，首先，as与与if连用连用，它的意思是：，它的意思是：“仿佛、好像仿佛、好像”同样引导从句。同样引导从句。1. 1. It isnIt isn t as if t as if we are richwe are rich(We are not rich(We are not rich) )我们不像富有的样子。我们不像富有的样子。(
7、 (即我们不富有即我们不富有) )2. 2. It isnIt isnt as ift as if he doesn he doesn t know the rulert know the ruler(i (ie eHe does know the rulersHe does know the rulers) )他不像不懂规则的样子。他不像不懂规则的样子。( (即他懂得规则即他懂得规则) )另外另外as if还可以引导还可以引导感叹句感叹句。 As ifAs if I would allow it!(i I would allow it!(i. .e eI would certainly no
8、t I would certainly not allow it!)allow it!)好像我会答应似的好像我会答应似的!( !(我才不会答应哩我才不会答应哩!) !)6其次其次, if与与only连用。常表示愿望或一个连用。常表示愿望或一个未实现未实现的的条件，尤其用于感叹句中条件，尤其用于感叹句中。 1. If only he arrives in time! 他若能及时到达就好了他若能及时到达就好了!2. If only she would marry me! 但愿她能嫁给我！但愿她能嫁给我！ 3. If only she had known about it!（But she didn
9、t know.） 她那时要是知道（但她不知道）这事就好了她那时要是知道（但她不知道）这事就好了!八、八、Whether 和和 if的用法区别的用法区别（一）引导宾语从句，一般既可用（一）引导宾语从句，一般既可用whether也可也可用用if。但。但 7A or not放在放在whether之后时，只能用之后时，只能用whether不不用用if。I dont know whether or not he will come. 我不知道他是不是回来。我不知道他是不是回来。注注1：如果：如果or not放在放在whether所引导的从句句尾，所引导的从句句尾，则可以用则可以用if来替换。来替换。I
10、dont know whether/if he will come or not.我不知道他是不是回来。我不知道他是不是回来。B 在强调任意选择时在强调任意选择时,用用whetheror,此时不用此时不用if替换替换whether。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。他问我是想乘火车还是坐公共汽车去那里。8C 虽引导宾语从句，但为了虽引导宾语从句，但为了强调强调宾语部分，也宾语部分，也可把从句放在句首，此时只用可把从句放在句首，此时只用whether不用不用if。Wheth
11、er he will come I am not sure.他是不是来我拿不准。他是不是来我拿不准。D 从句作介词宾语时只用从句作介词宾语时只用whether不用不用if。It depends on whether it will be fine.那那得看是不是晴天。得看是不是晴天。E 作作discuss等动词的宾语时，用等动词的宾语时，用whether不不用用if。We discussed whether we should close the shop.我们讨论是不是该关掉商店。我们讨论是不是该关掉商店。9F 句子中有句子中有if引导的条件句，如再有表示引导的条件句，如再有表示“是否是否”
12、的宾语从句，用的宾语从句，用whether不用不用if。He asked me whether Id move to New York if I got the job.他问我如果我得到那份工作是否会搬家到纽约。他问我如果我得到那份工作是否会搬家到纽约。G 容易产生歧义时用容易产生歧义时用whether不用不用if来表示来表示“是否是否”。Please let me know if you need help. 如果你需要帮如果你需要帮助请告诉我。或：请告诉我你是否需要帮助。对助请告诉我。或：请告诉我你是否需要帮助。对比：比：Please let me know if you need hel
13、p.请告诉我请告诉我你是否需要帮助。你是否需要帮助。10H 如果宾语从句为如果宾语从句为否定句否定句时，则只用时，则只用if不用不用whether。I dont know if it wont rain tomorrow.我不知道明天是不是会下雨。我不知道明天是不是会下雨。（二）在引导主语从句、表语从句、同位语从句（二）在引导主语从句、表语从句、同位语从句时一般用时一般用whether不用不用if。Whether it is true remains a question. (主语从句主语从句)那是不是真的还是个问题。那是不是真的还是个问题。The question is whether it
14、 is true. (表语从句表语从句)问题是是不是真的。问题是是不是真的。We have a doubt whether it is true. (同位语从句同位语从句) 我们怀疑那是不是真的。我们怀疑那是不是真的。11（三）用（三）用在动词不定式之前时用在动词不定式之前时用whether不用不用if。I dont know whether to go there at once. 我不知道是不是该立刻去那里。我不知道是不是该立刻去那里。121. The question has not been answered _ Taiwan will be included on the Olymp
15、ic torch relay route. A.that B.whether C.which D.if2. You have not yet answered my question _ I can join in the party tonight or not. A. whether B. if C. that D. which3 I d like to invite you to a party this evening. Thank you, but _ Ill be free I m not sure at the moment.A. while B. if C. when D. w
16、hether 4-What are you anxious about? -_A. If we succeed B.That we can succeed C. Do we succeed D.Whether we can succeedBADD135. Only when _ the painting _ decide _the painting is worth buying. A. he sees, he can ,whether B. does he see, can he, if C. he sees, can he ,whether D. sees he, he can,that6
17、. _ English is his favourite subject A. I asked him if B. I asked him that whether C. I asked him that D. I asked him which7. _ theyll go to the Summer Palace _ the weather. A. If; depends on B. Whether; depends upon C. Whether; depended on D. If; depended upon8.It isnt quite _ _ he will be present
18、at the meeting. A. sure; whether B. sure; if C. certain; whether D. certain; thatBACC141. If you _ to the party, youll have a great time. A. will go B. went C. go D. going2. It will be a long time _ Peter _ his work. A. since, has finished B. after, finishes C. when, will finish D. before, finishes.
19、3. What will father _ us from Japan? A. take B. bring C. carry D. make 4. Weifang is famous _ kites A. for B. to C. on D. withCDBA155 I _ her the answer if she _me. A. can tell, will ask B. will tell, will ask C. would tell, ask D. will tell, asks6. What are you going to do tomorrow? -Well go to the
20、 library tomorrow if it _. A. isnt rain B. rain C. wont rain D. doesnt rain7.Do you know when he will come back tomorrow?-Sorry, I dont know. When he _ back, Ill tell you. A. comes B. will come C. come D. may come 8. What will you do if you _ to the old folks home visit?A. go B. went C. going D. wil
21、l goDDAA169. If I eat _ food, Ill be very fat.A. too many B. many too C. too much D. much too10. Ill give the book to him if he _ here next Sunday.A. will come B. comes C. is coming D. came11. There _an English film in our school tomorrow.A. is going to have B. will have C. is going to be D. has12.
22、Could you tell us where _？ A. will the next Olympic Games held B. the next Olympic Games will be held C. would the next Olympic Games be held D. the next Olympic Games would be held13. When my mother returned last night, I _ a book. A. read B. am reading C. was reading D. am going to readCCCBB1714.
23、What _ you _ when it began to rain?A. do, do B. were, doing C. are, doing D. did, do15. Ill wake you up when he _back.A. will B. is going to come C. comes D. come CB18If you weeped for the missing sunset,you If you weeped for the missing sunset,you would miss all the shining starswould miss all the shining stars如果你为着错过夕阳而哭泣，那么你就如果你为着错过夕阳而哭泣，那么你就要错群星了要错群星了19
