一个关于Otherwise 的虚拟语气

问题描述:

一个关于Otherwise 的虚拟语气
Mary ____ my letter ;otherwise she would have replied before now.
A has received B ought to have received
C couldn't have received
D shouldn't have received
请问这个题目的前半句话与虚拟预期有关吗?
选什么呢.到你
怎么区分 otherwise 在虚拟语气中的用法呀
有说选C的 .
但D为什么不选呢?
他俩有什么区别吗?

是C
后半句,otherwise句是对过去的虚拟.前半句不是虚拟语气.
D不选.should 是对未来的虚拟,这里不通.或者,SHOULD解释为应该,也不通