祈使句无主语,主语you常省去; 谓语为动词原形,句首加don't变为否定; 朗读应当用降调,句末常标感叹号.比较 祈使句和陈述句陈述句：You sit down.你坐下来.祈使句：Sit down.坐下 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) (85)It is better to stay home than _A__ out.A.to go B.going C.go D.gone 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:(92)_B_ is a good form of exercise for both young and old.A.The walk B.Walking C.To walk D.Walk 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:(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.Whether to do it hasn’t been decided.What to do next is up to you.
