精选优质文档-倾情为你奉上概念：动词不定式由to+动词原形构成。这里的to是不定式标志，没有词义。不定式具有名词、形容词或副词的某些语法功能，又有动词的时态和语态的特点及作用。 可以做主语、宾语、宾语补足语、表语、定语、状语。一、作主语动词不定式作主语时，句子的谓语动词常用单数，其位置有以下两种： (1)把不定式置于句首。如： To get there by bike will take us half an hour. (2)用it作，把真正的主语不定式置于句后，常用于下列句式中。如： Itbeto do Its our duty to take good care of the old. It takes sb+some time+to do How long did it take you to finish the work? Itbebto do It is difficult for us to finish for swriting the composi
