1.The reason for all the changes being m

问题描述:

1.The reason for all the changes being m
1.The reason for all the changes being made ____to us yet.
A has not explained
B has not been explained
请问选什么,为什么?

B,主语是reason,being made是修饰changes的为什么是现在完成时的被动形式因为原因是被解释的,然后句子里有yet,表示现完