if条件句

条件状语从句是在复合句中作条件状语的句子。表示假如有从句的动作发生就会有主句的动作发生。条件状语从句常由连词if引导。 (一)连接词if

if如果，是引导条件状语从句的连接词，表示主句中动作发生的条件。

☞ If you get up early, you will catch the bus. 如果你早起的话，就能赶上那班公共汽车。 ☞ You must see the doctor if you are ill. 如果你生病了，就必须去看医生。 (二)if引导的条件状语从句的构成

构成方式为＂主句+if引导的条件状语从句＂或＂if引导的条件状语从句+主句＂。 ☞ I will go to his birthday party if he invites me.

=If he invites me, I will go to his birthday party. 如果他邀请我，我会去参加他的生日聚会。 (三)if引导的条件状语从句的时态

在一般情况下，如果主句表示将来的意义，从句用一般现在时表将来。常见的有以下几种： 1. 主句谓语中有will, shall, won’t 表示将来时，从句用一般现在时。

☞ You will be late for school if you get up late. 如果你起晚了，上学将会迟到。 ☞ If it rains tomorrow, we won’t go to the Great Wall. 如果明天下雨，我们就不去长城。 2.主句中含有can, may, must等情态动词时，从句用一般现在时。

☞ If I finish my homework, I can watch TV. 如果我完成了家庭作业，就可以看电视。 3.主句是祈使句，从句用一般现在时。

☞ Don’t forget to lock the door if you are the last one to leave. 如果你最后一个离开，别忘了锁门。 (四)同义句转换

if引导的条件状语从句可以转换成简单句，其方法如下：

1.借助＂祈使句+and/or+简单句＂。其中and表示句意顺承，or表示转折。 ☞ If you work hard, you’ll pass the exam.

=Work hard, and you’ll pass the exam. 如果你努力学习，你就会通过考试。 *2.借助介词with 或without来转换。 ☞ If you help me, I’ll finish my job soon.

=With your help, I’ll finish my job soon. 如果你帮我，我将很快完成我的工作。 ☞ If there is no water, fish may die.

=Fish may die without water. 如果没有水，鱼可能会死。

（2015广西崇左）You will be late for school ________ you don’t get up early.

A. but B. and C. if D. or

I. 用括号内所给单词的适当形式填空 1. If it rains tomorrow, I ________(stay) at home.

2. He will take a trip to Beijing if he ________(be not) busy next week. 3. Please tell Li Jun about it if he ________(come) back.

4. If you don’t wear your school uniform to the party, the teachers ________(not let) you in. 5. She ________(not go) shopping with her parents if it snows this afternoon. 6. If I see him again, I ________ (tell) him what you say.

7. What ___________(happen) if they don’t agree with each other? 8. If given more time, I _______ (do) it better. 9. What will he say if he ______ (find) out the truth?

10. If the train _______ (be) on time, it will be here in ten minutes. II. 同义句改写，每空一词

1. Study hard, or you won’t pass the exam.

If you study hard, you ________ ________ the exam. 2. Take a taxi, and you’ll catch the train.

________ you ________ a taxi, you’ll catch the train. 3. If you don’t help me, I can’t catch up with the others.

I can’t catch up with the others ________ ________ ________. III. 单项选择

1. Stop smoking, Joe! You ________ yourself if you keep on doing it like that! A. will kill

B. killed

C. kill

2. Why not look up the new word in a dictionary________ you don’t know it? A. if

B. that

C. though

3. The earth will be more and more beautiful if everyone________ his best to love it. A. try

B. tries

C. will try

4. There will be less pollution ______ more people use public transportation. A. but

B. unless

C. if

5. Learning to write is learning to think. You will know things more clearly _____ you write down. A. if

B. unless

C. or