什么时候动名词做主语呢?

动名词做主语的用法
动名词做主语往往表示经常性,习惯性的动作,在口语中也可以表示具体的动作.如:
Seeing is believing.
Helping her is my duty.
动名词
Talking mends no holes.
空谈无济于事.
Working with you is a pleasure.
和你一起工作是一种乐趣.
动名词做主语和不定式做主语一样,也可以用it作形式主语.如:
It's rather tiring walking around in a city.
不定式做主语往往表示具体的特别是将来的动作.如:
It's no use crying over spilt milk.
覆水难收.
He realized that to go on like this was wrong.
(指抽象动作)
(指具体动作)
【考例】
— What do you think made Mary so upset
— __________ her new bicycle.
(1997上海高考题)
A.As she lost__ B.Lost
C.Losing______ D.Because of losing
解析:losing her new bicycle是句子的主语,谓语made her so upset被省略,losing… 在此表示具体的动作.