we went up to see that was the matter 这句话为什么错?

问题描述:

we went up to see that was the matter 这句话为什么错?
我知道错在that 应该用what,

这里what引导宾语从句,在从句中充当主语.
而that引导宾语从句的时候,都是不做成分的,可以省略的,所以这里不能用that.