一、复习指南I.it代替前文提到过的事物,代替指示代词this,that或以下概念: 1.环境、情况、时间、季节、距离等。例如: —Who’s:making such a noise? —It must be the wind. 2.it作形式主语、形式宾语代替不定式、动名词、从句。例如: It’s not a good habit to stay up late. He made it clear that he was not interestedin this subject. First, the review guide I.it instead of the things mentioned in the previous article, instead of the demonstrative pronoun this, that or the following concepts: 1. Environment, situation, time, season, distance and so on. For example: - Who’s: making such a noise? - It must be the wind. 2. It is the subject of the form, the formal object instead of the infinitive, the gerund, the clause. For example: It’s not a good habit to stay up late. He made it clear that he was not interestedin this subject.