什么时候用动词不定式或现在分词作句子主语,最好附加几个例句!答:就只能用 不定式 ,如: (93) 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. ...