初中英语――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/canIf 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/shouldIf 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。

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" if " 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If条件状从句练习（）1.If you _____ to the party, you’ll have a great timeA. will goB. wentC. goD. going（）2.–What are you going to do tomorrow? –We’ll go to the library tomorrow if it ___.A. isn’t rainB. rainC. won’t rainD. doesn’t rain（）3. What will you do if you _____ to the old folk’s home visit?A. goB. wentC. goingD. will go（）4. If I eat ____ food, I’ll be very fat.A. too manyB. many tooC. too muchD. much too（）5. I’ll give the book to him if he ___ here next Sunday.A. will comeB. comesC. is comingD. came（）6. I ____ her the answer if she ____me.A. can tell, will askB. will tell, will askC. would tell, askD. will tell, asks7. We’ll go to the farm and help the farmers with the apple-picking if it ______ tomorrow.A. won’t rainB. will be rainyC. doesn’t rainD. isn’t raining8. There is going to _______ a sports meeting next week. If it ________, we’ll have to cancel it.A. be, will rainB. have, will rainC. be, rains9. Your teacher will be unhappy if you _______ to school late.A. comeB. will comeC. are comingD. came10．I don’t know if he ______. If he _______ , please let me know.A. comes, comesB. will come, will comeC. will come, comesD. comes, will come 11．You will stay healthy _______ you do more exercise, such as running and walking.A. ifB. howC. beforeD. where12.If she _______ here tomorrow, I will tell you.A. comesB. will comeC. comeD. came13. I’m waiting for my friend.__________, I’ll go shopping alone.A. If she comesB. If she doesn’t comeC. If she won’t come14. —Tom wants to know if you will have a picnic tomorrow. —Yes. But if it ______, we’ll play chess instead.A. will rainB. rainedC. is rainingD. rains15. If Tom _____ the game, we'll give him a surprise".A. winB. winsC. wonD. miming16. If there _______ no buying and selling of animals, there ______ no killing in nature.A. is; will heB. will be; will beC. is; isD. will be; is17. Fm waiting for my friend.________, I'll go shopping alone.A. If she comesB. If she won't comeC. If she doesn't come18.The students ____ have a sports meeting this weekend if it _____。

A. won’t; rainsB. will; rainsC. won’t; will rainD. are going to; is going to rain19. What will you do if you _____ to the old folk’s home visit?A. goB. wentC.goingD. will go答案1.c2.d3.a4.c5.b6.d7.d8.c9.a 10.c 11.a 12. a 13b 14.d 15.b 16.a 17.c 18.a 19a三．完成句子。

1.如果他到的晚了会发生什么事情？What ______ _____ if he ____ late?2. 如果努力学习，你就会取得好成绩。

If you______ _______, you _____ ____good _______.3. 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.4. 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.5.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.6. 如果她睡过头了，就会旅游迟到的。

he____ ___ ___ ___ the trip if she _____7. 如果他有空，他会帮助你的。