Grammar—the subject claus
语法—名词性从句之主语从句
、概述
在复合句中起主语作用的从句叫主语从句。
引导主语从句的关联词有从属连词that、whether，关系代词：who, what, which , whom, who, whatever, whoever, whomever, whichever；关系副词：when, where, how, why, however, whenever, wherever等。
含有主语从句的句子，谓语动词多用第三人称单数形式。语序为陈述语序。
That you don’t like him is none of my business.你不喜欢她不管我的事。
What he said is true.
Whether the football game will be played depends on the weather.
.分类详解
1.从属连词that，whether引导的主语从句。
从属连词that，whether在主语从句中的作用只是引导主语从句，它们在从句中不做成分，不能省略。
Whether she will come or not is still a question. 她是否会来仍是一个问题。
That they will go is certain.他们去是肯定的。
2.it作形式主语引导主语从句。
如果主语从句太长，为避免句子结构头重脚轻，常用it作形式主语，而把主语从句放在主句谓语部分之后。That引导的主语从句可用it代替，that 不可省略。
用作it作形式主语的结构：
(1).It is/was +形容词+that 从句
It’s natural that… 很自然…… It’s obvious that … 显而易见……
It’s fortunate that … 幸运的是 It’s (im)possible…（不）可能……
It’s unlikely that… 不可能 It’s strange that…奇怪的是……
(2).It is/was +名词+that 从句尿白蛋白高
It’s a pity that… 遗憾的是…… It’s a fact that …事实是……
It’s good news that…是好消息…… It’s a wonder that…不足为奇……
It’s an honour that… 非常荣幸…… It’s a shame that…真是可耻……
It’s common knowledge that … 是常识…
(3).It is/was +过去分词+that 从句
化归思想 It’s not known that… ……不得而知 It’s said that… 据说……
It’s reported that… 据报道…… It’s not decided that…尚未决定
It’s believed that… 据认为……罩杯测量 It’s announced that…据宣布……
It’s suddenly struck me that… 我突然想到（感觉到）……
(4).It +不及物动词+that 从句
It ems that… 似乎…… It happened that…碰巧……
It appears that…看来…… It turns out that…结果……
It occurs to me that…我突然想起……
(5).其他
It doesn’t matter … 是无关紧要的
It makes no difference …毫无区别……
It is of little conquence that…无关紧要
It is a pity that she has made such a mistake.
It's strange that he didn't come yesterday.
It is said that he has gone to Shanghai.(=He is said to have gone to Shanghai)
It ems that he has en the film.
It occurred to me that I failed in the examination.
It doesn’t matter whether he is wrong or not.
It makes no difference to me whether you go or not.
3、由关系代词引导的主语从句。
（1）关系代词who, what, which, whom, who, whatever, whoever, whomever, whichever等，引导主语从句时，它们分别在从句中担任主语、宾语或定语，不能省略。
Whoever leaves the room last ought to turn off the lights.
What you have done might do harm to other people.。
Who made the long distance call is not important.
（2）what引导主语从句“……的东西诽谤的意思/事情”时，可用来表示the thing(s)which这种意思，引导从句，表示一样东西与一件事情。 what，who，火锅涮羊肉whom，which，可以和ever构成合成词，和what一样引导从句，ever起强调作用。这些关系词在句子中充当成分，所以不能省略。此类主语从句不能用形式主语it引导。
What I need (=The thing which I need) is a mobile phone.
Whoever leaves the office (=Any one who leaves the office)should tell me.
4、关系副词引导的主语从句。
连接副词有when, where, why, how, however, whenever, wherever等引导主语从句时，它们在从句中担任状语，不能省略。此类主语从句可以转换为以it作形式主语的句子。
Why he didn't come here is not clear to anyone.
How a telephone works is a question which not everyone can answer.
日本龙三角
深圳香蜜公园Where she has gone is not known yet
When they will start has not been decided yet.。
Why he did it didn't concern me.
5、主语从句不可位于句首的四种情况。
（1）含主语从句的复合句是疑问句、感叹句时，主语从句不可提前，用引导词it作形式主语。
Is it really true that he has gone abroad?
How surprising it was that he failed in the exam!
（2）It is said, reported, …结构中的主语从句不可提前。
It is said that the play is very interesting.
It is reported that the highway will be opened to traffic next week.
（3）It happens, occurs…结构中的主语从句不可提前。
It occurred to her that she had forgotten to lock the door.
It happened that I met him in the street.
（4）It doesn’t matter how, whether or not…结构中的主语从句不可提前。
I t doesn’t matter whether he likes it or not
It doesn’t matter how he will come.
（5）if 引导的主语从句不可居于复合句句首。
(误)If Tom really trust me is still doubtful.
(正)It is doubtful if Tom really trust me.
(正)Whether Tom really trust me is still doubtful.
6、it作形式主语与it引导强调句的比较。
吉林省简称 it作形式主语代替主语从句，主要是为了平衡句子结构（特别是谓语较短时），主语从句的连词没有变化。而it引导强调句则是对某一句子成分的强调（这一成分可以是词、词组或句子），其结构是“It is(was)+ 强调成分+that”。无论强调什么成分，都要求用连接词that(强调人时可以用who代替)。
It is certain that she will succeed.（主语从句）
It is in New York that I met him.（强调句）
7.从句的否定前移
用作it形式主语,而将主语从句放在句尾说时，主语从句的否定词常要前移至主句中，例如：
It doesn’t em that they are from the same university.
It doesn’t appear that we will have a sunny day tomorrow.
8、语气
在It is necessary / natural / important / + that-clau这类句型里,that所引导的主语从句中谓语动词用"should +原形",表虚似语气.例如:
