[观察例句]
观察下列例句，体会其黑体部分的语法功能
1．Learning to understand and share the value system of a whole society cannot be achieved just in the home. 作主语
2．Taking exercise every morning helps make one healthy. 作主语
3．I consider waiting a bit longer before I give up. 作宾语
4．I can't imagine marrying such a woman. 作宾语
5．I kept studying English for 1 hour yesterday evening. 作宾语
[归纳用法]
1．动词ing形式作主语
(1)往往表示经常性、习惯性的动作，谓语动词用单数。
Swimming is my favourite sport.
游泳是我最喜欢的一项运动。
Collecting stamps is his hobby.
集邮是他的爱好。
[名师点津]
动词ing形式和不定式都可以作主语。动词ing形式作主语表示一般或抽象的多次行为，不定式作主语往往表示具体的或一次性的动作。作宾语时也是如此。
Playing with fire is dangerous.
玩火危险。(泛指)
Be careful！To play with fire will be dangerous.
小心点！玩火会带来危险。(指一具体动作)
(2)在It is no use/no good/useless/worthwhile/dangerous/a waste of time/fun等后需用动词ing形式作真正的主语，句首的it是形式主语。
It's no use waiting for him any longer.
再等他是没有用的。
It's a waste of time arguing about it.
争论此事就是浪费时间。
(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 joking about such matters.
这种事开不得玩笑。
