表语从句是什么？
就是把表语用句子代替!
表语从句用法小结
一、表语从句的定义：
表语从句放在连系动词之后，充当复合句中的表语。
二、表语从句的构成：
关联词+简单句
三、引导表语从句的关联词的种类：
1. 可接表语从句的连系动词有be，look，seem，sound，appear等。
China is no longer what she used to be.
今日的中国不再是过去的中国了。
The question remains whether they will be able to help us.
问题还是他们能否帮我们。
At that time，it seemed as if I couldn't think of the right word.
当时，我似乎怎么也想不出一个恰当的字眼来。
2. 从属连词whether，as，as if / though引导的表语从句。
He looked just as he had looked ten years before.
他看起来还与十年前一样。
It sounds as if someone is knocking at the door.
听起来好像有人在敲门。
3. because，why引导的表语从句。
That's because he didn't understand me.
那是因为他没有理解我。（That's because…强调原因）
That's why he got angry with me.
那正是他对我生气的原因。（That's why…强调结果）
what引导的主语从句表示结果或名词reason作主语时，后面的表语从句表示原因时要用that引导，不宜用because.
The reason why I was sad was that he didn't understand me.
我难过的原因是他没有理解我。
4. 连接代词who，whom，whose，what，which，whoever，whatever，whichever
连接副词 where，when，how，why
The problem is who we can get to replace her.
问题是我们能找到谁去替换她呢。
The question is how he did it.
问题是他是如何做此事的。
That was what she did this morning on reaching the attic.
那就是她今晨上了阁楼干的。
5. 从属连词that
The trouble is that I have lost his address.
麻烦是我把他的地址丢了。
6. 使用虚拟语气的表语从句
在表示建议、劝告、命令含义的名词后的表语从句，谓语动词需用“should+动词原形”
表示，should可省略。常见的词有：advice，suggestion，order，proposal，plan，idea等。
My suggestion is that we （should） start early tomorrow.
我的建议是我们明天一早就出发。
四、应注意的问题：
1. 连系动词be，appear，seem，look等之后可以跟表语从句。
It was because he didn't pass the exam.
那是因为他没有通过考试。
It seems（that）he was late for the train.
看来他没搭上火车。
It appears that she was wrong.
看来她错了。
It seems to me that we should answer for this.
在我看来，我们似乎应该对此事负责。
It appears to her that he wants to teach us all he has.
在她看来，他似乎要把他所会的都教给我们。
2. 引导表语从句的引导词有以下几类。
1）wh-疑问词
My question is who left.
我想问的是谁离开了。
What I wonder is when he left.
我想知道他是何时离开的。
That's what he wants.
那是他想要的。
This is where they once lived.
这就是他们曾经住过的地方。
That is why he didn't come here. 这就是他为何没到这儿来的原因。
2）whether
My question is whether he left（or not）。 我的问题是他是否离开了。
注：if不能引导表语从句。
3）that
The fact is that he left. 事实是他离开了。
注：引导表语从句的连词that间或可以省略。
The truth is（that）I didn't go there. 事实是我没去那儿。
4）because，as，as if，as though
It's just because he doesn't know her. 这是仅仅因为他不认识她。
Things are not always as they seem to be. 事物并不总是如其表象。
He looks as if he's tired. 他好像累了。