that与what引导名词性从句的区别

that与what引导名词性从句的区别
 
that引导名词性从句只起连接作用，在从句中不作任何成分，无意义，在宾语从句通常省略，但在主语从句、表语从句和同位语从句中均不能省略；what除引导从句外，还在从句中作成分，意为“所……的(东西)”，在含义上等于“名词+that”。如：
1. 用that的例子
That she lacks experience is obvious. 她缺少经验，这是显然的。http://yingyu.chazidian.com
The police learned that he wasn’t there at that time. 警察获知他那时不在场。
He realized that she too was exhausted. 他意识到她也精疲力尽。
My idea is that you shouldn’t have left the country. 我的意见是你不应该离开那个国家。
Bob has the mistaken idea that tomorrow is a holiday. 鲍勃错误地认为明天是一个假日。
It was quite plain that he didn’t want to come. 很明显他不想来。
It is natural that they should have different views. 他们看法不同是很自然的。
 
2. 用what的例子
What (=The thing that) he said was true. 他所讲的是事实。
What he had hoped at last came true. 他希望的事终于成为现实。
What he said is beneath contempt. 他说的话不值一理。
What he says is true, possibly. 或许他说的是对的。
What she saw gave her a fright. 她看到的情况吓了她一跳。
What I want to say is this. 我想说的是这一点。
I’m sorry for what I said. 我为我说的话表示歉意。
That’s what I want to know. 这是我想知道的。
You had better hear what I have to say. 你最好听听我的意见。
I managed to get what I wanted. 我设法得到了我要的东西。
It was what he meant rather than what he said. 这是他的原意而不是他的原话。
There’s something in what he says. 他的话有些道理。
Her interest was roused by what he said. 他的话引起了她的兴趣。
He was always conscious of the fact that she did not approve of what he was doing. 他一向清楚她不太赞成他的做法。
注：that 可引导同位语从句，what不能。如:
Have you any idea what time it starts? 你知道什么时候开始吗?