连接代词what的三种使用方法
引导名词性从句的what在从句中作主语、宾语、表语或定语。
(1)具备疑问代词性质的what：意为“什么，哪种”。如：
I don’t know what he needs. 我不了解他需要什么。(what在宾语从句中作宾语)
(2)在名词前表示感叹的what：意为“多么”。如：
only then did I recognize what silly mistakes I had made. 只不过在那时我才意识到我有多么愚蠢的错误。(what在宾语从句中作定语)
(3)具备关系代词性质的what：意为“所……的”。
等于“the＋名词＋that”或者all that，即仿佛是既包含了先行词也包括了关系代词，因此，有学者称之为关系代词型what。如：
What (=The thing that) happened after that was interesting. 后来发生的事挺有意思。(what在主语从句中作主语)
China is not what (=the China that) used to be. (what在表语从句中作表语)
The boy dived into water and after what (the time that) seemed to be a long time, he came up again. 他跳进水里，过了仿佛很长时间之后，他才又从水里出来。(what在宾语从句中作主语)
