It doesn't matter______he has come back or not.

问题描述:

It doesn't matter______he has come back or not.
A.if B.whether C.that D.when
本题选B,为什么不选A,是什么从句?

句意解释为他回不回来都没有关系.
If 后面要接or 的话,If就要变成whether.