先行词 it 在主语或宾语的位置，真正的主语或宾语是后面的不定式、动名词或名词性从句。 一、作形式主语 句型：It is+ adj. /n. + doing/to do…/that 从句 Is it necessary for me to do so? 我有必要这样做吗？ It is silly of him to do so. 他这样做真是可笑。 It’s no good waiting here. 在这里等没有用。 Is it certain that they will win? 他们一定会赢吗? It’s my duty to help you improve English. 帮助你们提高英语水平是我的职责。 二、作形式宾语 1. 句型：vt. (find, think, make, etc. ) + it +adj. /n. +doing/ to do/that… He made it a rule never to eat between meals. 他不吃零食已成了习惯。 I think it impossible for us to finish our work on time. 我认为我们不可能准时 完在这项工作。 We found it no good arguing with him. 同他争论是没用的。 I’ll make it clear to you that failure is the mother of success. 我要告诉你们失败的成功之母。 I’d think it well worth while to go. 我觉得很值得一去。 2.句型：vt. (enjoy, like, love, hate, prefer, appreciate, take, etc. ) +it+ if /when/ that… I don’t like it if you arrive late. 我不喜欢你迟到。 She hates it when he uses her pen. 她讨厌他用她的钢笔。 I take it that you have been out. 我猜你刚出去回来。 You can put it that it was arranged before. 你可以说这是以前安排的。(put=say) 3. 句型：take it for granted that…（理所当然地认为…） I took it for granted that you would stay with us. 我肯定你会住在我们这里的。