主语从句学习指要
用来作主语的句子叫做主语从句。如：
(1)when he was born is unknown. 他生于何时还不知道。
(2)what he did last night is being investigated. 他昨天晚上干了些什么正在调查之中。
在主语从句中须注意：
1. 主语从句一般用it作形式主语，放在句首，而将主语从句放到句末。如：
(1)it is possible that he has stolen the car. 很可能他偷了小车。
(2)isn’t it strange that he should not have passed the test? 他测试没有通过，难道不奇怪吗？
2. if引导主语从句时，只能用it作形式主语，放在句首，而将if引导的主语从句放到句末。如：
it is uncertain if he will leave for beijing tomorrow. 明天他是否去北京还不敢肯定。
3. that引导主语从句放在句首时，that不可省，但在句末口语中可省。如：
that he was ill yesterday is known now. 大家都已知道他昨天生了病。
4. 连接代词引导主语从句只能放在句首。如；
(1)who has broken the glass is unknown. 谁打破了玻璃现在还不知道。
(2)what he wants is all here. 他所要的东西都在这里。
5. 主语从句中主句的谓语动词一般用第三人称单数形式，但what引导主语从句的主句谓语动词的形式须根据句子的意思来判断。如(from )：
(1)how he worked it out is still a secret. 他是如何把它做出来的还是一个秘密
(2)what they makes in this factory are tv sets. 他们在工厂里所做的东西就是电视机。
主语从句用法详解(例句丰富)
一、主语从句的引导词
主语从句通常由连词that和whether、连接代词或连接副词以及关系代词型what引导。
1. that引导
that he is still alive is a wonder. 他还活着，真是奇迹。
that we shall be late is certain. 我们要晚了，这是确定无疑的。
that he should have ignored the working class was natural. 他忽视工人阶级是很自然的。
that she is still alive is a consolation. 她还活着是使人感到宽慰的。
that she became an artist may have been due to her father’s influence. 她成为画家可能是受她父亲的影响。
that you are coming to london is the best news i have heard this long time. 你将来伦敦是好久以来我听到的最好消息。
that she was chosen made a tremendous stir in her village. 她被挑选上，在她村 子里引起很大轰动。
2. whether引导
whether it will do us harm remains to be seen. 是否对我们有害还要看一看。
whether they would support us was a problem. 他们是否会支持我们还是一个问题。
3. 连接代词引导
whoever is top from wins the game when two matched players meet. 两强相争勇者胜。
whichever (of you) comes in first will receive a prize. 无论(你们)谁先到都可以得奖。
whichever you want is yours. 你要哪个哪个就是你的。
4. 连接副词引导
when we arrive doesn’t matter. 什么时候到没有关系。