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八年级英语：if引导的条件状语从句
引导条件状语从句最常用的连词是if，常见的if条件状语从句表示在某条件下，某事很可能发生，条件是可能存在的，主句中某种情况发生的概率也是很高的。如：
If you ask him，he will help you．如果你请他帮忙，他会帮你的。 If you fail in the exam，you will let him down．如果你考试不及格，你会让他失望的。
If you have finished the homework， you can go home．如果你作业做完了就可以回家了。
另外，if从句还表示不可实现的条件或根本不可能存在的条件，也就是一种虚拟的条件或假设。从句多用一般过去时或过去完成时，表示对现在或过去的一种假设。如：
If I were you，I would invite him to the party．如果我是你，我会邀请他参加聚会。
I would have arrived much earlier if I had not been caught in the traffic．要不是交通堵塞，我本会来得早一些。
另外你还要注意if 条件句的时态搭配
1． if从句用一般现在时，主句用一般将来时
If he runs he’ll get there in time. 如果他用跑的，他就会及时赶到那儿。
The cat will scratch you if you pull her tail. 如果你拉猫的尾巴，它就会抓你。
2． ．if从句用一般现在时，主句用may/might/can
If the fog gets thicker the plane may/might be diverted. 如果雾在大一些，飞机可能就会改在别的机场降落。
If it stops snowing we can go out. 如果雪停了，我们就可以出去。
3． if从句用一般现在时，主句用must/should
If you want to lose weight you must/should eat less bread. 如果你想减肥，你必须少吃面包。
4． if从句用一般现在时，主句用一般现在时
If you heat ice it turns to water. (也可用will turn)如果把冰加热，它就会化成水。
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5． if从句用现在进行时，主句用一般将来时
If you are looking for Peter you’ll find him upstairs. 如果你是在找彼得，上楼就会找到他。
6． if从句用现在完成时，主句用一般将来时
If you have finished dinner I’ll ask the waiter for the bill. 如果你吃完了，我就叫服务生来算账
注意 ：
学习\引导的条件状语从句的用法,现在总结一下: 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。 在 if 引导的条件状语从句中，如果从句谈论的是一个有可能发生的事实及其产生的相关的结果，主句用一般将来时态，从句用一般现在时态。如：
We can walk there if we can't find a bus .
If it rains tomorrow ,we will not go to the zoo. What will you do if you find a panda in danger.
如果 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 danger ,they attack people.
在 if 引导的条件状语从句中，if 和条件句位置灵活，可直接放在主句后面，若 if 条件句放句首， 从句后面要加逗号，和主句隔开。还要注意前后时态一致原则
一、用所给词的适当形式填空
1.If you ________(feel) tired, you _______________ (have) to have a rest.
3. If there __________(be) fewer trees, there _______________( be) more pollution. 5. If Marcia _____________(live) alone, she ___________________( keep) a pet parrot.
6. Lana ________________( buy) a new dress if the old one ____________(be) out of style.
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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.
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.
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.
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。
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. going
2. It will be a long time ____ Peter _____ his work.
A. since, has finished B. after, finishes C. when, will finish D. before, finishes.
3. What will father _____ us from Japan? A. take B. bring C. carry D. make 4. Weifang is famous ______ kites. A. for B. to C. on D. with 5． I ____ her the answer if she ____me.
A. can tell, will ask B. will tell, will ask C. would tell,
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ask D. will tell, asks
6. – What are you going to do tomorrow?
--We’ll go to the library tomorrow if it ___.
A. isn’t rain B. rain C. won’t rain D. doesn’t rain 7.—Do you know when he will come back tomorrow?
--Sorry, I don’t know. When he ____ back, I’ll tell you. A. comes B. will come C. come D. may come
8. What will you do if you _____ to the old folk’s home visit? A. go B. went C.going D. will go
9. If I eat ____ food, I’ll be very fat.
A. too many B. many too C. too much D. much too
10. I’ll give the book to him if he ___ here next Sunday. A. will come B. comes C. is coming D. came
11. There ____an English film in our school tomorrow.
A. is going to have B. will have C. is going to be D. has 12. Could you tell us where ____？ A. will the next Olympic Games held B. the next Olympic Games will be held C. would the next Olympic Games be held D. the next Olympic Games would be held
13. When my mother returned last night, I ____ a book. A. read B. am reading C. was reading D. am going to read 14.What ____ you ____ when it began to rain?
A. do, do B. were, doing C. are, doing D. did, do 15. I’ll wake you up when he ____back.
A. will B. is going to come C. comes D. come
1---5 CDBAD 6---10 DAACB 11---15 CBCBC
If条件状从句例题
【2011陕西】24. If there no buying and selling of animals, there no killing in nature. A. is; will he B. will be; will be C. is; is D. will be; is答案：A 【解析】考查点：本题考查if引导的状语从句的时态。if 意为“如果”。引导条件状语从句，主将从现。故选A。
【2011黑龙江绥化市】25. Fm waiting for my friend._, I'll go shopping alone.
A. If she comes B. If she won't come C. If she doesn't come 答案：C【解析】考查从句的时态。If引导的条件状语从句，主句用将来时，从句用一般现在时。根据句意：如果他不来，我就独自去购物。故选C。
【2011雅安】10.The students ____ have a sports meeting this
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weekend if it _____。A. won’t; rains B. will; rains C. won’t; will rain D. are going to; is going to rain答案：A【解析】考查if引导的条件状语从句用法。if意为“如果”，引导条件状语从句，主句用一般将来时，从句用一般现在时态。句意为“如果明天下雨我们就不举行运动会了”。故选A。
If从句如何考？
请看这道2006年河北省的中考题：
—Mike wants to know if________a picnic tomorrow.
—Yes. But if it________, we’ll visit the museum instead. A. you have; will rain
B. you will have; will rain C. you will have; rains D. will you have; rains 正确答案应该是C。为什么同样一个if，后面所接的时态却不相同呢？这要从if引导的条件状语从句说起。
条件状语从句表示主句动作发生的条件，在初中阶段常由if(如果)引导，表示假如有从句的动作发生就会有主句的动作发生。例如： Please call me if he is at home. 假如他在家的话，请给我打电话。
条件状语从句和主句还有一个共同的伙伴，有时它可以替代从句和主句，它就是“祈使句+and / or+简单句”。其中and表示句意顺承；or则表示转折，意为“否则”。例如：
If you work harder, you’ll pass the exam.
= Work harder, and you’ll pass the exam. 如果你再努力些，你就会通过考试。
If you don’t hurry up, you’ll miss the train.
= Hurry up, or you’ll miss the train. 如果你不快点儿，你就赶不上火车了。
在学习条件状语从句时，同学们要注意以下几点：
一、时态呼应
一般来讲，复合句都要遵循主、从句时态呼应规律，状语从句也不例外。即主句用现在时，从句也用现在时；主句用过去时，从句也用过去的某种时态。具体地讲，主句是一般现在时(包括祈使句和含有情态动词can, may, must等)，从句也用一般现在时。例如： Have a good rest if you are tired. 如果你累了，就好好休息一会儿吧。
You must see the doctor if you are ill. 如果你生病了，就必须去看医生。
这里提醒大家特别要注意：如果主句是一般将来时态，这时从句
。
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if引导的条件状语从句精讲与专题练习
