什么时候用不定式?什么时候用动名词?

什么时候用不定式?什么时候用动名词?

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动名词作主语与不定式作主语在语序位置方面较相似,但在表达意思上有差异.动名词作主语时,它已经将动作名词化了,已把某个动作视为某种活动或是某件事情了,动作意义很弱,比较抽象.而不定式作主语的动作意义较强,多指"要是去做某事",这种动作往往是"要发生的一次性动作",比较具体.例如：
Breathing became difficult at that altitude.
在那个海拔高度呼吸变得很困难.
Reading English aloud in the morning will do you a lot of good .
早晨朗读英文会给你带来许多好处.
Cheating on an exam ruins one's character .
考试作弊毁坏人的性格.
It takes me ten minutes to get home from my office .
我从办公室回家要花十分钟.
It needs time to make three copies of it .
把它复制三份需要时间.
动名词作主语时,也常用"It is …"和"There is …"两种句型.
"It is …"的句型常用于说明"某种活动或是某件事情是如何,如何".强调事物的性质、特征等.常用于It is后面的词有：no good , no use , useless , a waste, worthwhile , dangerous等等.句型"There is …"往往用于说明"不允许、禁止某种活动或是某件事情发生或存在".类似一种建议、命令等.例如：
It is no use waiting for him any longer .
等他是没有用的.
It is no good learning without practice .
学而不实践是没好处的.
It is dangerous using this method to measure the speed of light .
用这种方法去测量光速是危险的.
It is worthwhile consulting your tutor about it again .
很值得再向你的指导老师咨询一下这个问题.
There is no joking about such matters .
这种事开不得玩笑.
There is no denying the fact that China has made a rapid progress in every aspect since it was founded .
不容抵赖这个事实,中国自它成立以来已在各个方面都取得了飞速的发展.
There is no littering about .
不许乱扔杂物.