不定式作主语不定式直接自置于句首,或采用先行词,将不定式后置.to.pptVIP

 作主语 不定式直接置于句首,或采用先行词,将不定式后置. To hesitate is a pity.To be here is a great pleasure.It is a pity to hesitate.It’s a great pleasure to be here. 后置不定式结构也适用于谓语动词不是连系动词的句子。 It made me happy to find Mary there. Wouldn’t it be a pity to spoil your drawing? How exciting it was to fight a shark! 不定式结构作主语通常表示具体动作,间或也可表示抽象动作,这一点与-ing 分词结构作主语恰恰相反。 用作主语的不定式结构的逻辑主语通常可以在特定上下文或情景中看出,也可以由”for+名词词组”.间或也可用for+ there to be表示。 It is important for us to have a good grasp of English. It is a great pleasure for us to be here this evening . It’s a pity for there to be any disagreement in the family.（在这种结构中，there后面的不定式只能是to be） 不定式结构作主语 不定式在联系动词后作主语补语有两种情况：一种情况，主语和主语补语都是不定式，其含义一是条件，一是结果。 To see is to believe. To decide is to act. 另外一种情况，主语是以aim, ambition, duty, hope, idea, intention, mistake, plan, purpose, suggestion 等为中心的名词词组，或以what 引导的名词性分句，后面的不定式说明其内容。 My idea is to climb the mountain from the north. What I would suggest is to start work at once. 不定式结作主语补语时常带to，但在某些句型中可省略to，条件是主语部分必须具有一个动作动词do。 All I did was empty the bottle. The worst you can do is become very drowsy. The only thing I can do now is go on by myself. What I really wanted to do was drive all night.(也有人指出在由what引导的主语分句中，如果谓语词部分的do是完成体形式，后面的补语也可以用-ed，如果do是进行体形式，则补语必须用-ing 分词。) What he’s done is :spoil the whole thing . to spoil the whole thing . spoilt the whole thing . What he’s doing is spoiling the whole thing . All she seems to do is gossip with her neighbors. 不定式结构作动宾 ，能用带to不定式作宾语的有两种；一种是直接跟有带to不定式，另一种是跟有疑问词+带to不定式结构。 第一种常见的词有；afford, agree, aim, apply, arrange, ask, choose, claim, decide, decline, demand, desire, determine, expect, hope, learn, long, manage, offer, pretend, promise, refuse, seek, swear, threaten, want, wish ,etc. He agreed to smoke no more cigarettes. She applies to work only at weekends. afford通常与 can,此同时can’t或它们的过去时形式连用。如： We can afford to pay for it. We can’t afford to go away for a holiday this summer. 第二种