主语从句是什么意思

定义 在复合句中充当主语成分的句子叫做主语从句. 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. （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. （7）Who the watch belongs to was lost is unknown. （8）What we need is time. （9）What we need are good doctors. 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（9） 第二部分 为了防止句子头重脚轻，通常把形式主语it放在句首位置，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. （4）It is strange that he should do that. （5）It is important that we all should attend the meeting. （6）It is strange that the man should have stuck to his silly ideas. （7）It is a pity that we won't be able to go to the south to spend our summer vacation. （8）It is still a mystery what caused the accident. （9）It is said that he has gone to shanghai.(=He is said to have gone to shanghai) （10）It is known to all that the gun powder was first invented by the Chinese. （11）It is suggested that the work should be done with great care. （12）It happened that the two cheats were there. (=The two cheats happened to be there) 小结: （1）为避免头重脚轻,常以形式主语it引导从句. It+形式主语谓语+从句. （2）由于主语从句一般被认为是单数形式，形式主语的谓语 动词、be动词+表语 均为单数第三人称形式或过去式.

原本一句完整话的主语部分用一句话来代替,但需要三类引导词,且不能省略,一，that引导的陈述句。二，whether引导的一般疑问句（不能用if)。三，一系列wh词引导的特殊疑问句，要用陈述语序。例：That they are still alive is a consolation。所有名词性从句都是一样的思路

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