高中语法详解：名词遥从句中的主语从句名词遥从句包括：主语从句、表语从句、宾语从句和同位语从句。
引导名词遥从句的连词有： 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，且通常遥以省。
为了强调that引导的主语从句而置之于句首时，that遥省。
①That the driver could not control his car was obvious.
②That she was chosen made us very happy.
③That he will come is certain.
④That he would take the risk is true.
⑤That he should have married her isn't surprising.
★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.
②It made us very happy that she was chosen.
③It is certain that he will come.
④It is true that he would take the risk.
⑤It isn't surprising (that) he should have married her.
★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.
②It is strange that she has ever trusted him.
③It is important that he(should) attend the meeting.
④It is best that he (should) go.
此句型在表示惊讶、喜悦、遗憾等感遥彩时，that从句中的谓语动词也常用(should)+ v原形。
It is strange that no one should have objected to the plan.
(2)it + be +名词+ that-从句 It is common knowledge that the whale is not a fish.
.
.
It's a pity that he should have massed the train.
(3) it + be + -ed分词 + that从句 It is said that he is a famous writer.
It is reported that there will be a storm this afternoon.
▲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.
It is demanded that he (should) leave at once.
(4) it + seem/happen/appear等不及物动词+that从句。
(look不接that从句，它接to be结构或形容词) It seems that he is wrong.
It appears that they are in urgent need of help.
He looks (to be) surprised/happy/sad.
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.
Whether he will come is uncertain.
Whether she comes or not doesn't concern me.
It is not clear whether/if he will come.
It was uncertain whether he would come.