He didn't know the reason__she got angry.

问题描述:

He didn't know the reason__she got angry.
A for that B for which C of which D which为什么选B 不选A

介词+which 引导定语从句.
或者 that 引导定语从句,那要写成
He didn't know the reason that she got angry for.
没有介词+that的用法