同样是名词性从句的连词,what和which有什么区别

就是what与which的区别.
还有一个是what有纯名词性的,如：What he said is wrong.
which只能是由一个疑问句变来的名词性从句.
作为疑问代词what和which的区别是：
后者给定选择的范围.前者不限.
如：
Which do you like eat,A or 回答在A或B中选一个.
What do you like to eat?回答是开放性的.
两个词都可以作定语,后加名词如：
Which book do you want to buy?
What book do you want to buy?
问：什么叫纯名词性
不带疑问性质的=名词+that-定语从句的.
这是我发现的关于名词性从句的一个细节.
这种名词性从句作主语时,是不可以用it来代替而后置的.
比如：The books that I bought yesterday are very interesting.不能说成：It is very interesting the books that I bought yesterday吧?同理,What I bought yesterday is very expensive.不说：It is very expensive what I bought yesterday.
但是：What we should do next is still unclear.--> It is still unclear what we should do next.常这么说.