主语从句讲解

　　定义

　　在复合句中充当主语成分的句子叫做主语从句.

　　名词性从句(主语从句、宾语从句、表语从句和同位语从句) 中的连接词

　　连词: that / whether / as if (though);

　　连接代词: what / who/ which / whose / whatever / whoever / whomever / whichever，

　　连接副词: where / when / why / how / wherever / whenever

　　第一部分

　　常规主语从句，即句子在复合句中充当一个主语

　　主语从句的时态：不受主句的时态影响和限制。

　　（1）That he finished writing the composition in such a short time surprised us all.

　　that在主语从句中有三个特点：不作成分；没有词义；不能省略。

　　（2）Whether we will go for an outing tomorrow remains unknown.

　　（3）Who will be our monitor hasn't been decided yet.

　　（4） Whom we must study for is a question of great importance.

　　（5）What caused the accident remains unknown.

　　（6）Whatever you did is right. （主语从句大部分情况看成第三人称单数形式）

　　（7）What we need is time.

　　（8）What we need are good doctors. （主语从句有时可以根据表语来判断单复数问题）

　　小结:

　　（1)引导主语从句连词有that, whether, who, what, whatever等

　　（2)连词位于句首不能省略

　　（3)主语从句大多数情况下视为第三人称单数,但也有例外,如例（8）

　　第二部分

　　为了防止句子头重脚轻，通常把形式主语it放在主语位置，真正主语搁置于句末

　　（1）It is certain that he will win the match.

　　（2）It is true that he has made a very important discovery in chemistry.

　　（3）It is very likely that they will hold a meeting.