iii. 条件状语从句

1. 当主句是一般将来时时，条件状语从句必须用一般现在时表将来。

We'll hold a sports meeting next Sunday if it is fine.

如果下周日是晴天我们将举行运动会。

2. If表示正面的条件，unless表示反面的条件，unless=if ... not。

I shall go there tomorrow if it doesn't rain.

如果明天不下雨我就去那里。

I shall go there tomorrow unless it rains.

我明天要去那里除非天下雨。

3. if可以引导虚拟条件句，其他连词不可以。

If I were you , I would not have followed his idea.

若我是你，我当初是不会听从他的建议的。

4. if only引导的从句谓语必须用虚拟语气。only if“只有”，从句用陈述语气，主句语序须倒装。

If only I were studying in a famous university now!

若我现在就在一所名牌大学学习该多好啊！

Only if you work hard can you pass the college entrance examination.

只有努力学习，你才能通过大学入学考试。

5. so/as long as意为“只要”。

As （So) long as you keep on trying , you will surely succeed in the end.

只要你坚持尝试，你最终就一定能成功。

6. supposing that= suppose that表示假设。

Supposing that it rains , I won't come to school tomorrow.

假如天下雨，我明天就不上学了。

7. providing (that) = provided (that)意为“如果，只要”。

You may come providing (that) you are allowed.

许你来你就来。

I will go with you, provided (that) my expenses are paid.

只要有人给我出钱，我就同你一起去。

8. on condition that表示“以……为条件”。

You can do anything well on condition that you put your heart into it.

只要你把全部身心投入进去，就能做好任何事情。

9. in case= for fear that意为“以免，以防”。

Take an umbrella with you in case it snows .

带上雨伞吧以免天下雪。

10. given that意为“倘若考虑到……”。

Given that he is only a child, he has done very well.

倘若考虑到他还是个孩子的话，他已经做得很好了。

11. 可与含有if条件状语从句的复合句进行转换的两个句型：

1）祈使句/名词短语+ and/or +简单句

Think hard and you'll have a good idea.

=If you think hard, you'll have a good idea.

仔细想一想你就会有好办法的。

2）分词+简单句

Thinking hard, you'll have a good idea.

仔细想一想，你就会有好主意的。

12. 当will, shall用于条件从句中时，不表示将来时间，而表示现在的意愿、意图等。

If you will listen to me , I'd like to give you a suggestion.

如果你愿意听我说，我想给你提一条建议。

专项练习

1. I think our boat can pass the treacherous water _______ cautiously handled.

A. until

B. if

C. lest

D. with

2. I'll give you a lift _______ I get home _______ you get off.

A. before; if

B. after; as

C. if; before

D. until; before

3. You'll succeed in time _______ you study hard.

A. unless

B. as long as

C. even if

D. even though

4. The robber told him that he had better keep silent _______ he wanted to get into trouble.

A. if

B. unless

C. otherwise

D. whether

5. I have made a promise _______ anyone can tell me the secret, I'll give him a little present.

A. that if

B. that

C. when

D. so long as

6. Don't let her leave the department _______ she is not ready to.

A. if

B. though

C. unless

D. till

7. I wrote these words down _______ I should forget.

A. for

B. so

C. lest

D. since

8. We are sure to do the work well _______ we don't lose heart.

A. for

B. so long as

C. as if

D. since

9. He would be punished _______ he should make the same mistake again.

A. unless

B. if

C. provided

D. lest

10. Anyone can borrow books from this library _______ he keeps them clean and returns them in time.

A. even if

B. unless

C. so that

D. as long as

11. _______ you return those books to the library immediately, you will have to pay a fine.

A. Until

B. Unless

C. If

D. Provided

12. The parents did not allow their son to swim in the sea _______ he might have an accident some day.

A. for fear that

B. in case of

C. besides

D. and that

13. It is a gripping story and one can't put it down _______ one has finished reading it.

A. after

B. when

C. unless

D. until

14. They agreed to rent the house　 _______ the roof should be repaired.

A. on condition that

B. as soon as

C. when

D. unless

15. The more civilized man has become, _______ he is limited by the disadvantage of his environment.

A. and the more

B. the less

C. test

D. and the less

答案速查　1-5　BABBA　6—10　ACBBD　11—15　BADAB