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
网友回答
A. has received
B. ought to have received
(答案→)C. couldn’t have received
D. shouldn’t have received
解析：考查情态动词用法。关键后半句：要不然，她之前就会给我回信。根据这里的would have replied可知是对过去情况的虚拟，那么前一句也应该是对过去情况的推测。结合句意可知C正确。句意：玛丽不可能收到我的信得。要不然之前就会给我回信的。