if引导的条件状语从句和宾语从句

1、If的用法if的条件从句分为真实条件从句和虚拟条件从句。真实条件从句：真实条件从句适用于主将从现，是假设有可能发生的。.位置在if引导的条件状语从句中，既可以放在主句之前，也可以放在主句之后。若if条件句放句首，从句后面要加逗号，和主句隔开。You will catch the bus if you get up early. = If you get up early, you will catch the bus.二. 时态1. （主祈从现）主句：一般现在时态（包含祈使句和含有情态动词can, may, must等的句子）从句：一般现在时态2. （主将从现）主句：一般将来时态从句：一般现在

2、时态3. 从句：现在进行时，主句：一般将来时If you are looking for Peter you ' find him upstairs.如果你是在找彼得，上楼就会找到他。4. if从句用现在完成时，主句用一般将来时If you have finished dinner I ' ask the waiter for the bill.如果你吃完了，我就叫服务生来算账5.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 dan ger ,they attack people.三. 注意事项1. 在if

3、引导的条件状语从句中，当主句是一般将来时态时，不能使用be going to结构,而要用will.2. 在if引导的条件状语从句中，不能使用some而要用any.四. 同义句转化1. 借助于祈使句+and / or+简单句转化，and表示顺承，or表示转折。例如：（1）lf you work hard, you 'llpass the exam.Work hard, and you 'lpass the exam.（2）If you do n'hurry up, you 'llbe late.Hurry up, or you 'll be late.2.

4、 借助于介词 with或者without来转换例如：If you help me, I 'll finish my job soon.With your help , I 'llfinish my job soon.内容从句与现在事实相反动词过去式（be用were）与将来事实相反should/were to+ 动原与过去事实相反had+过分虚拟条件从句：虚拟条件从句是假设不太可能发生的。IF的虚拟语气有三种：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。主句would/could/should/mi

5、ght+ 动原 would/could/should/might+ 动原 would/could/should/might+ have+ 过分 下面三句依次是上面三种情况的例句：If I were you ,I would/could/should/might do that.If I had know that yesterday, I would/could/should/might have told you .If it should rain , the crops would/could/might be saved.If引导的宾语从句一. if引导宾语从句时，意思为：是否，从句的

6、时态通常要和主句保持一致。【例句】 I want to know if he lives there. 我想知道他是否住在那儿。He asked me if I couldhelp him.他问我是否能帮他。【考查点】if、whether引导的宾语从句的区别1. 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。【例句】 Nobody knows whether / if it will rain tomorrow.没有人知道明天是否下雨。Lucy asked whet

7、her / if they had a cott on sweater.露西问他们是否有棉制的毛衣。二. 注意事项：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既不能和that或其他连词(副词)同时使用，也不能省略。【例句】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.他走过来看看猫是否出了毛病。误He came to see wh

8、at if (whether) there was anything wrong with his cat .正He came to see if (whether) there was anything wrong with his cat .2.if或whether引导宾语从句时，虽具有疑问的意义，但其从句应用陈述句的语序。【例句】 Did you know the way to the hospital? The old woma n asked me.The old woma n asked me if / whether I knew the way to the hospital.

9、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，从句用任一种时态； 主句为一般过去时，从句则用过去时中的任一种时态。【例句】 I don ' t know if (whether) he has come here.我不知道他是否来过这儿。Tom asked if (whether) I had read the book.汤姆问我是否看过这本书。三. If和whether两者不能互换的情况1. 只能用whether的情况在动词不定式之前只能用whether:【例句】I can' t decide whethe

10、r to stay.我不能决定是否留下。2. 在whetheror not的固定搭配中：【例句】I want to know whether it ' s good news or not. 我想知道它是不是好消息。3. 在介词后，只能用 whether:【例句】His father is worried about whether he loses his work.他的父亲担心他是否会失去工作。4. 用if会引起歧义时：【例句】 Could you tell me if you know the an swer? 这句话有两种意思："你能告诉我你是否知道答案吗？”或“如果

11、你知道答案，请告诉我，好吗？”。如用whether则可避免歧义。【考题链接】I don ' t knowthey could pass the exam or not.A. why B. ifC. that D. whether答案：D 解题思路：本题考查if与whether的区别，在 whetheror not的固定搭配中通常 只用 whether。练习题：句型转换1. Do they want fried chicken? He asked the boys.(改为宾语从句)He asked the boystheyfried chicke n.2. Was the watch m

12、ade in Shanghai? I don' t know.(改为宾语从句)I don' t knowthe watchmade in Shanghai.3. “ Do you want to try something new? ” Tom' s mother asked him.(同义句转换 )Tom' s mother asked himto try something new.答案：1. if / whether, wan ted 2. if / whether, was 3. if / whether he wan ted一、用所给词的适当形式填空1

13、f you(feel) tired, you(have) to have a rest.3. If there(be) fewer trees, there( be) more polluti on.5. If Marcia(live) alone, she( keep) a pet parrot.6. Lana( buy) a new dress if the old one(be) out of style.9. Peter( send) me a beautiful souve nir if he(tour) Spain.10. If Mr Gree n(say) I am hard-

14、work ing, my pare nts( feel) glad.11.I(go) to the beach if it( not rain) this week.13. He(write) a letter to his gran dpare nts if he(get) his report card this week.14. If she(get) up late, she( not catch) the early bus.15. Peter(major) in En glish if he(pass) the exams in Pek ingUn iversity.16. 如果努

15、力学习，你就会取得好成绩。If you, yougood.17. 他如果看电视太久了，他的父母会不高兴。If heTV too much, his pare ntsun happy.18. 如果我们为他组织生日聚会，大家都会来的。Every oneif wea birthday partyhim.19. 如果明天不下雨，我会和你一起去公园的。If ittomorrow, Igo to the parkyou.21.如果他有空，他会帮助你的。If he, he you.23.你如果抄同学的作业就不能学好各门功课。Yougood at all the subjects if youthe othe

16、r students homework.I单项选择（1f youto the party, you ' have a great time.A. will go B. went C. go D. going2. It will be a long timePeterhis work.A. since, has finished B. after, finishes C. when, will finish D. before, finishes.3. What will fatherus from Japa n?A. take B. bring C. carry D. make4. W

17、eifang is famouskites.A. for B. to C. on D. with5. Iher the answer if sheme.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?-We llgo to the library tomorrow if it.A. isn ' rain B. rain C. won' rain D. doesn ' rain7.

18、Do you know whe n he will come back tomorrow?-Sorry, I don ' know. When heback, I ' tell you.A. comes B. will come C. come D. may come8. What will you do if youto the old folk ' home visit?A. go B. went C. going D. will go9. If I eatfood, I ' be very fat.A. too many B. many too C. too much D. much too10. I ' give the book to him if hehere n ext Sun day.A. will come B. comes C. i