If 用法汇总1、主将从现 （主句为一般将来时,从句为一般现在时）；eg:If it rains(从句) ,I will stay at home（主句）.=I will stay at home if it rains.2、主句含有情态动词 （must、may、can etc.）从句为一般现在时；eg:If you drive too fast ,you may have an accident.=You may have an accident if you drive too fast3、主句为祈使句,从句要用一般现在时态；eg:Dont play computer games if you dont finish your homework.4、 是否=whetherAsk if he is at home. I wonder if she is ill.5、 虚拟语气 eg:If I were a bird ,I would fly in the sky.（事实我不可能是鸟）时态：可以表示过去，现在和将来的情况，它的基本特点是时态退后.a.同现在事实相反的假设从句用一般过去时 should( would) +动词原形If they were here,they would help you.b.表示于过去事实相反的假设从句用过去完成时 should(would) have+ 过去分词If she had worked harder,she would have succeeded.If my lawyer had been here last Saturday,he would have prevented me from going.c.表示对将来的假想一般过去时 ，were+ to do， 从句：主+ should/would/could/might+v原形should+ v原形，If you succeeded,everything would be all right.If you were to succeed,everything would be all right.If you should succeed,everything would be all right.单项练习（每个必须让学生翻译）1. If I _ where he lived, I _ a note to him.A. know, would have sentB. had known, would have sentC. know, would send D. knew, would have sent2. Mary is ill today. If she _, she _ absent from school.A. were not ill; wouldnt be B. had been ill; wouldnt have beenC. had been ill; should have been D. hadnt been ill; could be3. He acted as if he _ everything in the world.A. knew B. knows C. has known D. wont know4. If you had enough money, what _?A. will you buy B. would you buyC. would you have boughtD. will you have bought5. If Mr. Young _ with justice, he _ such a wrong thing.A. were treated; wouldnt doB. had been treated; wouldnt have doneC. were treated; wouldnt have doneD. had been treated; wouldnt do6. What _ if there _ no light during the day?A. will happen; wasB. would happen; isC. happens; were D. would happen; were7. The spokesman acted that way as if he _ anything about the accident but actually he did.A. doesnt hear B. didnt hear C. havent heard D. hadnt heard8. If it _ not for the fact that you _ ill now, I would surely punish you.A. is; are B. were; were C. were; are D. was; were9. Many Chinese movie stars now have given up their Chinese nationality. If I were them,I _ that.A. shouldnt do B. didnt do C. hadnt done D. wont do10. I want to get back by 5 oclock if _.A. likely B. can C. possible D. Probable11. It seems as if it _ already summer now but it is only February.A. is B. was C. were D. had been12. If Henry had not pulled his cap low over his brow, he _ by the police.A. might be recognized B. might have been recognizedC. would have recognized D. was to have been recognized13. There is a ring at the door. That _ be the postman, I suppose.A. will B. wouldC. is going toD. was going to14. Look at the dark cloudsthere _ be a storm.A. will B. must have beenC. is going toD. would15. Why are you taking the pictures down?I _ the wall.A. paint B. have just paintedC. am going to paint D. will have painted16. Can I stay at home tomorrow?Yes, you can if it_.A. will snow B. is going to snowC. snows D. snowed17. I dont know if he _ this afternoon. But if he _, I will tell you.A. will come; will do; B. comes; will doC. will come; does D. comes; does18. I thought I asked you to fix the radio.Oh, Im sorry. I _ it right away.A. am to do B. will doC. was about to doD. am going to do19. The WTO cant live up to its name _ it does not include a country that is home to one fifth of mankind.A. as long as B. whether C. if D. even though20. Ask him to ring me up if you _ him.A. see B. saw C. would see D. will see21. Its so late. I dont think he _ come.A. would B. should C. is going to D. shall22. If people _ polluting the air, animals and plants will die soon.A. dont stop B. didnt stopC. shall not stopD. havent stopped23. If you _ an interesting day out, _ the Science Museum.A. want; visiting B. want; visitC. want to; visit D. wanting; visit24. If the pure water is heated to 100 centigrade degrees, it _ boil.A. is going to B. will C. would D. is to25. Is a dictionary available, _ so, where?A. if B. if is C. and if D. and if is15 BAABB 610 DDCAC 1115 CBACC 1620 CCBCA 2125 CABBC最后一练1.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. af