which 和 what 在从句中的用法

题目

which 和 what 在从句中的用法
1.Output is now six times what it was before liberation.
2.They are so alike that you can't tell which is which.
想请教一下为什么这么用?不是说what用在名词从句里,而which单独时用在形容词不是说what用在名词从句,which单独时用在形容词从句吗?
第一句为什么不是‘which it was before liberation’ 来修饰times,做形容词从句?
第二句为什么不是‘what is which ’做tell的宾语从句,which能做从句的主语吗?不是what才能做从句的主语吗?

答案

WHAT he says is true==SOMETHING THAT he says is true
She showed me WHAT she had bought== She showed me the THINGS THAT / WHICH she had bought.