1.主语从句:What is beautiful is not always good.
美的东西并不总内是好的。
2.宾语从句:I could hardly believe what he had told me.
我简直不敢相信他所告诉我的。
3.表语从句:Books are what we need most.
书是容我们最需要的东西。
4.同位语从句:I have no idea what he is doing.
我不知道他正在做什么。
一、that引导从句时不充当句子成分(定语从句除外),what引导从句要充当句子成分(比如主语、宾语等)。如:
1. We believe that he is honest. 我们相信他是诚实的。(that在此不充当句子成分)
2. We believe what he said. 我们相信他说的话。(what在从句中用作动词said的宾语)
二、在通常情况下,介词(except,but,in等少数介词除外)后面可以接what引导的从句,但不能接that引导的从句,所以下面句子中的what均不可换成that,因为它们所引导的从句是用作介词的宾语:
1. He always stands for what is right. 对于正确的东西他总是支持的。
2. I’ll pay you back for what you did to me. 你对我做的那些事我要进行报复。