If 用法汇总及练习.doc

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 fast 3、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. 是否=whether Ask if he is at home. I wonder if she is ill. 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 sent　　　　　B. had known, would have sent C. know, would send 　　　　 　　D. knew, would have sent Mary is ill today. If she _____, she _____ absent from school. A. were not ill; wouldn’t be　　 B. had been ill; wouldn’t have been C. had been ill; should have been 　　　D. hadn’t been ill; could be 3. He acted as if he _____ everything in the world. A. knew 　　B. knows 　　　C. has known 　　　D. wont know 4. If you had enough money, what _____? 　　A. will you buy 　　　　　　　　B. would you buy 　　C. would you have bought　　　　D. will you have bought 5. If Mr. Young _____ with justice, he _____ such a wrong thing. 　　A. were treated; wouldn’t do 　　B. had been treated; wouldn’t have done 　　C. were treated; wouldn’t have done 　　D. had been treated; wouldn’t do 6. What _____ if there _____ no light during the day? 　　A. will happen; was　　　　B. would happen; is 　　C. happens; were　　　　　 D. would happen; were 7. The spokesman acted that way