初中主语从句讲解

主语从句

名词性从句包括：主语从句、表语从句、宾语从句和同位语从句。引导名词性从句的连词有：

A.连词：that, whether, if（这三个词都不作从句的成分，同时，that 无含义，而whether和if都表“是否”）

B.疑问代词：who, whom, whose, what, which

C.疑问副词：when, where, why, how

（一）主语从句：在复合句中充当主语的从句。

1.that引导主语从句

that引导主语从句时不同于其他的连词，既无词义也不作成分，只起单纯的连接作用，且通常不可以省。为了强调that引导的主语从句而置之于句首时，that不可省。

①That the driver could not control his car was obvious. 很明显司机不能控制住他的车了

②That she was chosen made us very happy. 她被选上让我们很高兴

③That he will come is certain. 他要来已经千真万确了

★通常，that引导主语从句时用it做形式主语，把从句置于句尾，此时that有时可省。例如：

①It was obvious that the driver could not control his car. 很明显司机不能控制住他

②It made us very happy that she was chosen. 她被选上让我们很高兴

③It is certain that he will come. 他要来已经千真万确了

★如果以that从句为主语的句子是疑问句，就只能用先行词it结构。例如：

①Is it certain that he will come?

②Is it true that he would take the risk?

▲it做形式主语有以下几种不同的结构：

(1)It + be + 形容词+ that-从句

①It is likely that he will come. 他可能会来

②It is strange that she has ever trusted him. 她相信他，真令人奇怪

(2)It + be +名词+ that-从句

It is common knowledge that the whale is not a fish. 鲸鱼并不是鱼，这是常识

It's a pity that he should have catched the train.

(3) It + be + -ed分词+ that从句

It is said that he is a famous writer. 据说他是个著名作家

It is reported that there will be a storm this afternoon. 据报道下午将有一场暴风

▲在表示建议、要求、命令等意义的被动结构中，that从句中的谓语动词常用(should) do。（参见虚拟语气部分）

It is suggested that the meeting (should) be held this afternoon. 会议被

建议在下午举行

It is demanded that he (should) leave at once. 他被要求立即离开

(4) It + seem/happen/appear等不及物动词+ that从句。

It seems that he is wrong. 看起来似乎他错了

It appears that they are in need of help. 看起来他们需要帮助

2. whether引导主语从句，意为“是否”，只起连接作用，不充当任何成分。（置于句首时必须用whether引导，置于句尾时，间或可用if。）Whether he will win the game is not clear. 他是否会赢得比赛还不清楚。

Whether he will come is uncertain. 他是否会来还不确定

It is not clear whether/if he will come.

It was uncertain whether he would come.

3. 连词代词what, who, which, whose等引导的主语从句。这些连接代词作用相当于代词，在从句中担当主语、宾语、表语、定语等。What we need is more time. 我们需要的是更多时间

Who was responsible for the accident is not yet clear. 谁应该对这场事

故负责还不清楚。

Whose book it is not important. 这是谁的书并不重要。

Which school you want to go matters much. 你想去哪所学校很重要4.连接副词when, where, why, how引导的主语从句。这些连接副词相当于副词，在从句中充当状语。

Why he did this is not known. 他为什么做这件事还不知道。

When he will come is still unknown. 他什么时候来还不知道。

It is not known why he did this. 他为什么做这件事还不知道

注意：wh-引导的主语从句也常用it作形式主语。

5.也可用whatever,whoever,whomever,whenever,wherever等词引导主语从句，表示“无论什么”、“无论谁”、“无论何时”、“无论在（到）哪里”等。

Whatever he gave you should be handed in. 他无论给你什么都要上交Whoever told you that was lying. 无论谁告诉你，那都是撒谎Whoever comes is welcome. 无论谁来都是欢迎的