if引导的条件状语从句
[课本链接]
If you do, you’ll be sorry. (Unit 5, Section A)
[定义] :if引导的条件状语从句表示假如从句的动作发生，主句的动作就（不）会发生。 [句子结构]
if 引导的条件状语从句位置灵活，可直接放在主句后面，也可以放在句首。放在句首时，从句后面要用逗号和主句隔开。如：
I’ll go to see you if I have time. 如果有时间，我就去看你。
If it rains tomorrow, we’ll stay at home. 如果明天下雨，我们就呆在家里。 [时态呼应]
在复合句中：⑴ 当主句是一般现在时或是一般将来时时；（2）当主句是祈使句时；（3）当主句含有情态动词时，if引导的条件状语从句通常用一般现在时。
用 法 ① 主句为一般将来时态，if从句用一般 现在时态。（主将从现） ② 主句中含有情态动词，if从句用一般现在时态。（主情从现）如：may/might/can/could/must/should/would ③ 主句为祈使句，if从句用一般现在时态。 （主祈从现） ④ 主句为一般现在时时态，if从句用一般现在时态。（主现从现） Don’t jump into the river if you feel very hot. 如果你感到很热，不要跳入河里。 It’s dangerous if you play with the knife. 玩儿刀是危险的。 例 句 We will stay at home if it rains tomorrow. 如果明天下雨，我将要呆在家。 If you finish your homework, you can go home now.如果你做完了作业，你现在可以回家了。 如：
If she doesn’t come, she will be sorry. 如果她不来，她会遗憾的。 Have a good rest if you are tired. 如果累了，你就好好休息一下。
We must study hard if we want to pass the final exam. 如果想通过期末考试，我们必须努力学习。 [同义句转换]
1. 用“祈使句 ＋ and / or ＋ 一般将来时的句子”转换。如：
If you work hard, you’ll pass the exam easily. → Work hard, and you’ll pass the exam easily. 努力学习，你将很容易通过考试。
If you don’t hurry up, you’ll miss the train. → Hurry up, or you’ll miss the train.
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快点儿，否则你就赶不上火车了。
2. 用含介词with或without的介词短语转换。如：
If there is no water, fish can’t live. → Fish can’t live without water. 离开水，鱼不能生存。
【边学边做】
1. 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 2. The students ____ have a sports meeting this weekend if it _____.
A. won’t; rains B. will; rains C. won’t; will rain D. are going to; is going to rain 3. If you _____ to the party, you’ll have a great time. A. will go B. went C. go D. going
4.--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 5. If I eat ____ food, I’ll be very fat.
A. too many B. many too C. too much D. much too 6. I’ll give the book to him if he ___ here next Sunday. A. will come B. comes C. is coming D. came 7. Your teacher will be unhappy if you _______ to school late. A. come B. will come C. are coming D. came 8. I don’t know if he ______. If he ________, please let me know. A. comes, comes B. will come, will come C. will come, comes D. comes, will come 9. If she _______ here tomorrow, I will tell you.
A. comes B. will come C. come D. came
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10. —Tom wants to know if you will have a picnic tomorrow. —Yes. But if it ______, we’ll play chess instead.
A. will rain B. rained C. is raining D. rains 11. If Tom _____ the game, we'll give him a surprise\". A. win B. wins C. won D. miming 二、用所给词的适当形式填空。
1. What will you buy if you ________（have）a lot of money? 2. If it ________（not snow）tomorrow, we will feel unhappy. 3. You mustn’t go to school if you ________（be）still in bed. 4. If he _______（be）at home at that time, he would know it. 5. Please show me the way if you ________（know）it.
6. You will hurt your teeth if you ________（eat）too much candy. 7. If you gave me a toy car, I _________（be）very happy. 8. I would get the prize if I _________（work）hard.
9. Where _____ he ____ (see) the film if he _________ (have) time? 10. If there _______ (be) fewer trees, there _______ (be) more pollution.
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