概念引入
英国前首相撒切尔夫人(Margaret Thatcher)曾用if条件句对男人和女人进行评价:
In politics, if you want someone to make a speech, ask a man; if you want something done, ask a woman. 在政治领域,如果你想要有人发表演说,那就找男士去;而如果你想真正把事情解决,那就找女士。
用法讲解
一、概念
连词if的意思是“如果”,它引导的句子表示某事发生所需要的条件,即“在……条件下某事才能发生”,在句子中充当状语,因此我们称之为条件状语从句。在复合句中连词if引导的句子为从句,被修饰的句子为主句。从句可以放在主句后,也可以放在主句前,从句放在主句前时,应用逗号将它与主句隔开。例如:
We’ll go to the Great Wall if it doesn’t rain tomorrow. = If it doesn’t rain tomorrow, we’ll go to the Great Wall. 如果明天不下雨,我们就去长城。
二、用法
1. 条件状语从句通常由连词if引导,意为“如果,假如”,主句不能用be going to 表示将来,而应该用shall或will。例如:
If I’m free tomorrow, I’ll go with you. 如果我明天有空,我将会和你一起去。
2. if引导的条件状语从句,主句用一般将来时,从句则用一般现在时,即“主将从现”。例如:
If it is sunny tomorrow, I’ll climb the hill. 如果明天天气晴朗,我将去爬山。
3. 正确区分if引导的条件状语从句和if引导的宾语从句。
在条件状语从句中,if表示“如果”;而在宾语从句中,if表示“是否”。可以用下面的方法区分:
1) 从句前置法:if引导的条件状语从句,可以放在主句之前并用逗号隔开,也可放在主句之后;而if引导的宾语从句只能放在主句之后。因此如果把if放在主句之前,句子通顺,意义不变,则是条件从句,否则是宾语从句。例如:
He will help you if you ask him. = If you ask him, he will help you.
如果你问他,他会帮助你。
2) whether替换法:if引导宾语从句时,其意为“是否”,通常可用whether替换,意义不变,而if引导条件状语从句时不能用whether替换。因此,可用whether替换的是宾语从句,不能替换的是条件从句。例如:
I want to know if you will go tomorrow. = I want to know whether you will go tomorrow.
我想知道你明天是否去。
注意:区分if的用法有着极为重要的意义,因为在条件状语从句中,主句用将来时,从句用一般现在时;而在宾语从句中,当主句是一般现在时,从句可用所需的任何时态,主句是一般过去时,从句用过去的某种时态。
巩固练习
一、单项选择
1. If you _____ to the party, you’ll have a great time.
A. will go
B. went
C. go
D. going
2. I ______ her the answer if she _____ me.
A. can tell, will ask
B. will tell, will ask
C. would tell, ask
D. will tell, asks
3. — 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
4. — 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
5. I’ll give the book to him if he ____________ here next Sunday.
A. will come
B. comes
C. is coming
D. came
6. There ____________ an English film in our school tomorrow.
A. is going to have
B. will have
C. is going to be
D. has
7. I’ll wake you up when he ____________back.
A. will
B. is going to come
C. comes
D. come
8. The football match will be put off if it ________.
A. will rain
B. rains
C. rained
D. is rained
9. There ________ a basketball game this afternoon.
A. is going to have
B. will be
C. is going to play
D. will play
10. I won’t go if it ________ tomorrow.
A.rain
B.is raining
C.rains
D.will rain
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 ________ (go) to 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) not 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.
三、完成句子
1.如果他迟到了,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. 如果我们为他举办生日聚会,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,就会误了开会的。
She _______ _______ _______ _______ the meeting if she _______ _______.
7. 如果他有空,他会帮助你的。
If he _______ _______, he _______ _______ you.
8. 如果Tom考试不及格,他就没有机会上高中了。
Tom _______ miss the chance to go to the high school if he _______ the exams.
9. 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.
参考答案
一、单项选择。
1. C。本题是if引导的条件状语从句,主句用一般将来时,从句用一般现在时,即“主将从现”,所以答案为C。
2. D。根据句意“如果她问我,我就告诉她答案。”可知本句是if引导的条件状语从句,主句用一般将来时,从句用一般现在时,从句的主语为单三,动词后加-s,所以答案为D。
3. D。条件状语从句,主句用一般将来时,从句用一般现在时,rain在此是实义动词“下雨”的意思,故答案为D。
4. A。根据“主将从现”可知本句答案为A。此题是when引导的时间状语从句。
5. B。根据“主将从现”可知答案为B。
6. C。be going to do,will do都可以表示将来的动作,但只有选项C符合There be句型要求。
7. C。根据“主将从现”可知答案为C。
8. B。根据“主将从现”可知答案为B。
9. B。本题考查there be句型的一般将来时,there will be,故答案为B。
10. C。根据“主将从现”可知答案为C。
二、用所给词的适当形式填空
1. feel; will have
2. will; see; has
3. are; will be
4. will dress; doesn’t work
5. lives; will keep
6. will buy; is
7. will fight; argue
8. will have; need
9. will send; goes
10. says; will feel
11. will go; doesn’t rain
12. Will; have; is
13. will write; gets
14. gets; won’t catch
15. will major; passes
三、完成句子
1. will happen; is
2. study hard; will get; grades
3. watches; will be
4. will come; have; for
5. doesn’t rain; will; with
6. will be late for; sleeps late
7. has time; will help
8. will; fails 9. won’t be; copy