在句子中做条件状语的从句称为条件状语从句。
引导条件状语从句的连接词有：if ,unless,as/so long as，once等1.if引导的条件状语从句表示在某种条件下某事很可能发生。
If we pay much attention to the earth, we'll have a better world.如果没有水会怎样？2.unless引导的条件状语从句You will fail in English unless you work hard.3.as /so long as引导的条件状语从句So long as you're happy,i will be happy.4.once引导的条件状语从句Once you begin,never stop.提示：在条件状语从句中，用一般现在时代替一般将来时，用一般过去时代替过去将来时。
Father told me if i worked hard he would buy me a gift.if 条件状语从句的时态练习二、用所给词的适当形式填空1.If you ________(feel) tired, you _______________ (have) to have a rest.2. Where _______ he _________(see) the film if he ________________(have) time?3. If there __________(be) fewer trees, there _______________( be) more pollution.4. He _____________(dress) more casually if he ________________( not work) on weekends.5. If Marcia _____________(live) alone, she ___________________( keep) a pet parrot.6. Lana ________________( buy) a new dress if the old one ____________(be) out of style.7.The twins ______________(fight) if they_______________(argue).8. I ____________(have) a bake sale if I _____________(need) money for education.9. Peter _____________( send) me a beautiful souvenir if he ________________(tour) Spain.10. If Mr Green ___________(say) I am hard- working, my parents _________( feel) glad.11.I ____________(go) to the beach if it________________ ( not rain) this week.12. __________they __________( have) a match if the P.E. teacher _____________(be) busy?13.He ____(write) a letter to his grandparents if he ____(get) his report card this week.14. If she ____________(get) up late, she _____________ ( not catch) the early bus.15. Peter ________(major) in English if he ____(pass) the exams in Peking University.15.如果他到的晚了会发生什么事情？What _______________ if he _____________ late?16. 如果努力学习，你就会取得好成绩。
If you__________ _________, you ___________ good _____________.17. 他如果看电视太久了，他的父母会不高兴。
If he _________ TV too much, his parents __________ __________ unhappy.18. 如果我们为他组织生日聚会，大家都会来的。
Everyone ________________ if we _____________ a birthday party __________ him.19. 如果明天不下雨，我会和你一起去公园的。
If it __________ __________ tomorrow, I ______________ go to the park _________ you.20. 如果她睡过头了，就会旅游迟到的。
She;__________________________ the trip if she ___________________.21. 如果他有空，他会帮助你的。
If he _________________, he _________________ you.22. 如果Tom考试不及格，他就没有机会上高中了。
Tom _________have the ________to go to the ________high school if he ________ the exams.23. 你如果抄同学的作业就不能学好各门功课。
You _______ _____ good at all the subjects if you ______ the other students’ homework. Ⅰ.单项选择（15分）1.If you _____ to the party, you’ll 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 finishedB. after, finishesC. when, will finishD. before, finishes.3. What will father _____ us from Japan? A. take B. bring C. carry D. make4. Weifang is famous ______ kites. A. for B. to C. on D. with5．I ____ her the answer if she ____me.A. can tell, will askB. will tell, will askC. would tell, askD. will tell, asks6. – What are you going to do tomorrow?--We’ll go to the library tomorrow if it ___.A. isn’t rainB. rainC. won’t rainD. does n’t rain7.—Do you know when he will come back tomorrow?--Sorry, I don’t know. When he ____ back, I’ll tell you.A. comesB. will comeC. comeD. may come8. What will you do if you _____ to the old folk’s home visit?A. goB. wentC.goingD. will go9. If I eat ____ food, I’ll be very fat.A. too manyB. many tooC. too muchD. much too10. I’ll give the book to him if he ___ here next Sunday.A. will comeB. comesC. is comingD. came11. There ____an English film in our school tomorrow.A. is going to haveB. will haveC. is going to beD. has12. Could you tell us where ____？A. will the next Olympic Games heldB. the next Olympic Games will be heldC. would the next Olympic Games be heldD. the next Olympic Games would be held13. When my mother returned last night, I ____ a book.A. readB. am readingC. was readingD. am going to read14.What ____ you ____ when it began to rain?A. do, doB. were, doingC. are, doingD. did, do15. I’ll wake you up when he ____back.A. willB. is going to comeC. comesD. come。