一道单项选择题:that ? what?

A
因为the price是先行词，that引导的是定语从句。
what引导的是名词性从句，因此what前面不能有名词

That was the thing that he did.
That was what he did.

What I heard was different from what I saw.
The thing that I heard was different from the thing that I saw.

a

that,这里是定语从句，你可以把关系代词 that 还原到定语从句中charge the price for another product是为某物付钱。

在这里,what = the price that