不定式和动名词都可在句子中作主语,一般说来,有下面几点须给予注意：\x0d(1) 不定式一般表示具体的、特定的行为；而-ing分词一般表示抽象的、一般的行为.如：\x0dTo complete the program needs much effort.完成这项计划需要很大的努力.\x0dRiding a bike can make a man smart.骑单车能使一个人敏捷.\x0d(2) 在疑问句中,只能用动名词的复合结构作主语.如：\x0d(3) 在某些句型中通常要用动名词短语作主语.如：It is no use doing…/ It is no good doing… / It is useless doing…/ It is worthwhile doing…如：\x0dIt is no use talking your trouble to a man like him.跟他那样的人谈你的烦恼没有用.\x0d(4) 一般说来,作主语和表语的非谓语动词形式应一致,即：或同时为不定式,或同时为-ing分词.如：\x0dSeeing is believing.眼见为实.\x0d但是,在现代英语中,当表语用来说明主语的特定意义或具体内容时,主语和表语的非谓语动词的形式可以不一致,即,主语用动名词,而表语用动词不定式.如：\x0dWaving your hand is to say “Good-bye”.挥手就是说“再见”.\x0dNodding your head is to say “Yes”.点头就是说“对,是的”.
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第1个回答 推荐于2016-04-03
to do,有将来的含义，一次性的动作。
doing表示长时间，多次的行为，动作的进行。本回答被提问者和网友采纳
doing表示长时间，多次的行为，动作的进行。本回答被提问者和网友采纳
第2个回答 2015-04-11
to do动词不定式和doing动名词
第3个回答 推荐于2016-03-06
一、.动名词和不定式做主语的相同点
1. 不定式短语和动名词做主语时，常常为了保持句子的平衡，用it来做形式主语。如：
It is not easy to learn English well.
It is no use asking him for help.
2. 如果主语用了不定式，表语和宾语也要用不定式；主语用了动名词，表语和宾语也要用动名词，这在英语中称为对称性。如:
To see is to believe. = Seeing is believing. (眼见为实)
It is better to stay home than to go out.
二、动名词和不定式做主语的不同点
1. 不定式做主语常表示具体的某一动作，表示泛指或一般的抽象的概念时，多用动名词。如:
Walking is a good form of exercise for both young and old.
2.在”There/It +be+ no use(good/help/need)”之后常用动名词做主语，而少用不定式。如:
It /There is no use crying over the split milk.
It /There is no help taking this medicine.
但是，如果该句型中用了for引出不定式的逻辑主语，就只能用不定式。如:
There is no good for us to do that exercise.
3. 不定式可以和when, where, how, what, whether等连用，在句子中做主语，宾语和表语，而动名词则不能。如:
How to solve the problem is a hot potato.
Where to put the box seems hard to decide.
Whether to do it hasn't been decided.
What to do next is up to you.
1. 不定式短语和动名词做主语时，常常为了保持句子的平衡，用it来做形式主语。如：
It is not easy to learn English well.
It is no use asking him for help.
2. 如果主语用了不定式，表语和宾语也要用不定式；主语用了动名词，表语和宾语也要用动名词，这在英语中称为对称性。如:
To see is to believe. = Seeing is believing. (眼见为实)
It is better to stay home than to go out.
二、动名词和不定式做主语的不同点
1. 不定式做主语常表示具体的某一动作，表示泛指或一般的抽象的概念时，多用动名词。如:
Walking is a good form of exercise for both young and old.
2.在”There/It +be+ no use(good/help/need)”之后常用动名词做主语，而少用不定式。如:
It /There is no use crying over the split milk.
It /There is no help taking this medicine.
但是，如果该句型中用了for引出不定式的逻辑主语，就只能用不定式。如:
There is no good for us to do that exercise.
3. 不定式可以和when, where, how, what, whether等连用，在句子中做主语，宾语和表语，而动名词则不能。如:
How to solve the problem is a hot potato.
Where to put the box seems hard to decide.
Whether to do it hasn't been decided.
What to do next is up to you.
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