Period Three　Grammar，Speaking & Writing

一、动词­ing形式作主语

1.动词­ing形式作主语往往表示经常性、习惯性的动作，谓语动词用单数形式。

Swimming is my favourite sport.

游泳是我最喜欢的一项运动。

动名词和不定式作主语的区别：

动名词 动名词作主语表示经常性、习惯性的动作 Lying is wrong.撒谎不对。 不定式 不定式作主语表示具体的或一次性动作 To lie to her is wrong.对她撒谎不对。

2.形式主语it代替动词­ing形式作主语。

此类句式常见的有：

It's a waste of time doing sth.做某事是浪费时间。

It's useless/worthwhile doing sth.做某事没用/是值得的。

It's no good/use/fun doing sth.做某事没好处/没用/没意思。

It is a waste of time trying to persuade him to give up smoking.

想说服他戒烟完全是浪费时间。

It is worthwhile reading such a wonderful novel.

读这样一本精彩的小说很值得。

It is no use waiting for other people to make decisions for you.

等别人替你做决定是没有用的。

3.当句型"There is no..."表示"不允许、禁止某种行为的发生或存在"时，需用动词­ing形式作主语。

There is no denying that the environment is from bad to worse.

不能否认环境状况正在逐步恶化。

There is no joking about such matters.

这种事开不得玩笑。