If 用法汇总及练习

If 用法汇总

1、主将从现（主句为一般将来时,从句为一般现在时）；

eg:If it rains(从句) ,I will stay at home（主句）.

=I will stay at home if it rains.

2、主句含有情态动词（must、may、can etc.）从句为一般现在时；eg:If you drive too fast ,you may have an accident.

=You may have an accident if you drive too fast

3、主句为祈使句,从句要用一般现在时态；

eg:Don't play computer games if you don't finish your homework. 4、是否=whether

Ask if he is at home. I wonder if she is ill.

5、虚拟语气

eg:If I were a bird ,I would fly in the sky.（事实我不可能是鸟）

时态：可以表示过去，现在和将来的情况，它的基本特点是时态退后.

a.同现在事实相反的假设

从句用一般过去时should( would) +动词原形

If they were here,they would help you.

b.表示于过去事实相反的假设

从句用过去完成时should(would) have+ 过去分词

If she had worked harder,she would have succeeded.

If my lawyer had been here last Saturday,he would have prevented me from going.

c.表示对将来的假想

一般过去时，

were+ to do，从句：主+ should/would/could/might+v原形should+ v原形，

If you succeeded,everything would be all right.

If you were to succeed,everything would be all right.

If you should succeed,everything would be all right.

单项练习（每个必须让学生翻译）

1. If I _____ where he lived, I _____ a note to him.

A. know, would have sent

B. had known, would have sent

C. know, would send

D. knew, would have sent

2.Mary is ill today. If she _____, she _____ absent from school.

A. were not ill; wouldn’t be

B. had been ill; wouldn’t have been

C. had been ill; should have been

D. hadn’t been ill; could be

3. He acted as if he _____ everything in the world.

A. knew

B. knows

C. has known

D. won't know

4. If you had enough money, what _____?

A. will you buy

B. would you buy

C. would you have bought

D. will you have bought

5. If Mr. Young _____ with justice, he _____ such a wrong thing.

A. were treated; wouldn’t do

B. had been treated; wouldn’t have done

C. were treated; wouldn’t have done

D. had been treated; wouldn’t do

6. What _____ if there _____ no light during the day?

A. will happen; was

B. would happen; is

C. happens; were

D. would happen; were

7. The spokesman acted that way as if he _____ anything about the accident but actually he did.

A. doesn’t hear

B. didn’t hear

C. haven’t heard

D. hadn’t heard

8.If it _____ not for the fact that you _____ ill now, I would surely punish you.

A. is; are

B. were; were

C. were; are

D. was; were

9. Many Chinese movie stars now have given up their Chinese nationality. If I were them,I _____ that.

A. shouldn’t do

B. didn’t do

C. hadn’t done

D. won’t do

10. I want to get back by 5 o’clock if _____.

A. likely

B. can

C. possible

D. Probable

11. It seems as if it _____ already summer now but it is only February.

A. is

B. was

C. were

D. had been