i. 不定式作主语和表语

To think of you makes me old.

想你使我变老。

To see one time is better than to hear a hundred times.

眼见一遍胜过耳听百遍。

1. 口语中常用it作形式主语。

It takes me thirteen minutes to get to school from home.

从家到学校要花我13分钟。

It made me angry to hear him talk like that.

听到他那样说让我愤怒。

2. 若说明不定式动作对于执行者的影响，常在不定式前加for sb.。

It is not hard for us to learn English well in six years.

六年内学好英语对我们来说不算难。

It is a great honor for me to be present at the meeting.

我很荣幸来出席这个会议。

3. 但是以表示人的行为品质的形容词作表语时（如kind, good, nice, wise, clever, silly, wrong, right, foolish, stupid, careless, considerate, rude, naughty, polite, agreeable），不定式前加of sb.。

It's very kind of you to come and help us.

你真好来帮助我。

It's nice of you to be so considerate.

你这么体贴人真好。

4. 不定式作表语，表示目的、结果、同意、命令、安排、决定、劝告等意义。

His wish is to be a doctor .

他的愿望是当大夫。

They are to marry next week.

他们计划下周结婚。

My job is to teach you English.

我的工作是教你英语。

5. 用it作形式主语，其真正的主语也可以是for + there to be结构。

It was a pity for there to be any disagreement in the family.

家庭有不一致的观点是很遗憾的事。

6. 当主语和表语都是不定式时，其含义一是条件，二是结果。

To see is to believe .

眼见为实。

7. 不定式作表语时，主语也常是what引导的名词性从句，表语说明其内容。

What he is considering is to get enough money to buy a car.

他在考虑的是搞到足够的钱买辆车。

8. 不定式作表语时，主语部分有行为动词do，不定式也可省略to。

What he wants to do now is （to） find a good job.

他现在想做的是找到一份好工作。

专项练习

1. How _______ the problem will be discussed some time later this afternoon.

A. to solve

B. to be solve

C. being solved

D. solving

2. Is it necessary _______ the geography book at once?

A. for her to return

B. that she must return

C. her returning

D. of him to return

3. It _______ forty-five minutes _______ there by bus.

A. costs; to get

B. costs; getting

C. takes; to get

D. takes; getting

4. This grammar point is _______ later.

A. to explain

B. to have been explained

C. to be explained

D. to be explaining

5. Tom seemed _______ the good news.

A. to learn

B. to be learning

C. to have learned

D. to have been learning

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