if条件状语从句If 引导的条件状语从句If 引导的条件状语从句表示“如果… , 假如…”，表示在某种条件下某事可能发生。

含有if引导的条件状语从句的复合句由主句和从句构成。

If引导的是完整的句子，一定要有主语，称为从句，另一个句子称为主句。

句子结构：1. 祈使句/ 主句（will do ）/ 主句（can / must / should 等+do）+if条件状语从句2. if条件状语从句, + 祈使句/ 主句（will do ）/ 主句（can / must / should 等+do）1. Drop in on me if you have time . = If you have time , drop in on me .2. I will help you do housework if I finish my homework earlier .= if I finish my homework earlier , I will help you do housework .3. Y ou must study hard if you want to pass the exam . = If you want to pass the exam , you must study hard .特别注意：（1）上述情况下，条件状语从句必须用一般现在时态表示将来动作。

不可用一般将来时。

（2）if条件句和”祈使句+and / or+简单句”句型的转换Hurry up , or you’ll be late .= If you don’t h urry up, you will be late .Go straight ahead , and you will find the post office . = If you go straight ahead , you will find the post office .(3) unless 引导条件状语从句，可以和if转换。

unless（如果不，除非）= if … not …I won’t go to her birthday party unless she invites me .专项练习：1. ______ my watch if your watch ______ . A. Look at ; isn’t workB. Look at ; doesn’t workC. Look ; worksD. Look ; doesn’t work2. Please get up early _____ you want to catch the first bus .A. orB. becauseC. andD. if3. ______ to lock the door if you _____ the last one to leave .A. Forget ; areB. Don’t forget ; will beC. Forget ; will beD. Don’t forget ; are4. If you _____ to stay healthy , ____ some exercise every day .A. want ; doB. wants ; doesC. will want ; doD. will want ; does5. _____ your mother the truth , if you don’t like it .A. T ell B. To tell C. Telling D. Tells6. If you have something important to tell us , _____ it right now ! A. speak B. talk C. tell D. say7. If you ______ to the music , buy a CD . A. will listen B. listenC. listeningD. listened8. Be careful if you ______ want to make mistakes . A. won’tB. don’tC. didn’tD. not9. If you ____ a chance to study in a foreign country , just take it .A. getting B. had got C. will get D. get10. All of us will be happy _____ you can come with us . A, while B. if C. but D. or11. If Mr. Smith ____back , please let me know . A. will comeB. comesC. comeD. had come12. I am waiting for my friend. _______ , I’ll swim alone .A. If he doesn’t comeB. If he won’t comeC. If he will comeD. If he is coming13. I’ll go to the zoo if it _____ tomorrow .A. doesn’t rain B. will rain C. rains D. won’t come14. If you___ another programme , ___ this button .A. choose ; pressB. chose ; pressC. chose ; to pressD. choose ; pressing15. Hurry up , _____ you’ll miss the last bus .A. orB. ifC. soD. then16. I won’t finish washing the dishes before 7:00 , ____ you _____ help me .A. unless ; /B. if ; don’tC. when ; /D. A or B17. --- ______ if he leaves school this afternoon ? ---- The teacher will punish him .A. What will happenB. What happensC. What happenedD. What is happening18. If he ____ again , you should report him to the police .A. stealB. stealsC. stoleD. stolen19. ____ it is sunny tomorrow, I’ll go hik ing with my son .A. WhenB. AfterC. IfD. Whether20. What should I do _____ the machine ______ ?A. if ; doesn’tworkB. whether ; doesn’t workC. unless ; workD. after ; work句型转换：（同义句转换1-5）1. If you don’t come home early , your parents will be angry ._______ _________ early , _____ your mother will be angry .2. If you keep studying , you may join us one day . ____ studying , ____ you may join us one day .3. We can’t finish the work on time if you don’t help us . We can’t finish the work on time _____ you help us .4. Be careful when you cross the street , or you will be in dangerous .Y ou will be in danger _____ you _______ careful when you cross the street .5. I won’t go to her birthday party if she doesn’t invite me .I won’t go to her birthday party ____ she _______ me ./ I will go to her birthday party _____ she _____ me .6. Y ou copy Tom’s homework . Y our teacher will punish you .(合并为一句)________________________________________________________________ ____7. The computer has a virus . The computer doesn’t work . (合并为一句)________________________________________________________________ ____适当形式填空：1. If she ______ ( run) every day , she will be much stronger .2. If you _____ ( be) late for school , your teacher _____ （be）angry .3. If Mary ______ (win)the prize , her parents will be proud of her .4. If Tom _____ ( not do ) it , his brother ______ (do) it .5. We _____ ( get) into trouble if the workers _______ ( not help ) us .6. Please _______ ( tell ) me if you _______（go）.7. I _______ ( leave) for Beijing if it ________ ( not snow) this afternoon .8. If it _______（not rain）tomorrow , _____（let）us go shopping .9. If I get up late tomorrow , I _______ (be)late for school .10. Please bring your ID card . If you ______ (not bring) your ID card , you can’t go to the party .11. If he _____ (offer) to help mewith my English , I’ll be very happy .12. Mother told me if I ______ ( do) something wrong I should say sorry to her .13. If it ______ (snow) tomorrow , we’ll build a snowman .14. If somebody _______ ( wait) for you , you may go now .15. If he ______ (go) to the party , I _______ ( go) , too .16. Could you tell me if my father ______ ( arrive) home on time ?17. If my father _____ ( have) t ime tomorrow , he’ll take me to the zoo .18. _____(visit) the place if you _____ ( are ) interested in it .19. If you have a cold , _____ ( drink) water as much as possible .20. If you _____ ( not be ) happy , _______ ( try) ______( listen) to your favourite music .。