中考必备语法 主语从句&表语从句(共25张PPT)

主语从句，表语从句 在复合句中充当句子主语的从句叫主语从句。 【要点精讲】 一、whether, who, what, which, when, where, how, why等都可引导主语从句。如： Whether we will go for an outing tomorrow remains unknown. What I need most now is more time. 二、that引导主语从句时，that在句中不作句子成分，且无实际意义。当that引导的主语从句置于句首时，that不能省略；如果用it作形式主语，而把主语从句放在句末时，that可以省略。 如： That I will take an English test next week is certain. It is a pity (that) you made such a careless mistake. 三、it作形式主语的几种常见句型 ①It + be + n. +主语从句。常用于此句型中的名词有fact, rule, pleasure, truth, pity等。如： It is a fact that English is being accepted as an international language. ②It + be + adj. +主语从句。常用于此句型中的形容词有true, important, necessary, clear, certain等。如： It's true that the earth is round. ③It + v. +主语从句。常用于此句型中的动词有seem, appear, happen, follow等。如： It appears unlikely that interest rates will fall further. ④It + be +动词-ed形式+主语从句。常用于此句型中的动词-ed形式有known, said, proved, asked, suggested等。如： It's well known that Thomas Edison invented the electric lamp. 注意：if和whether都可引导主语从句，但if不能引导位于句首的主语从句。但如果用it作形式主语，而把主语从句放在句