表语从句：从句在复合句中充当表语
1， that引导的从句
The fact is that he can run fast 事实就是他能跑得很快
2， Whether 引导时
What I don't know is whether he can come here tomorrow 我所不知道的就是他明天是否能来这里
The question is whether you can solve it yourself 问题就是你是否能自己解决它
3， as if ，as though 引导时，可以用于虚拟语气
It looks as if he should clean the room 看起来他应该打扫这个房间
It looks as though he is right 看起来他是对的。
4， 其他连接词引导时
This is what I want 这个就是我想要的
This is who I want to find 这个就是我想要找到的人
This is why I come here 这个就是为什么我来这里
5， because 引导时
I believe it is because you are so tall 我相信这是因为你太高了。
