问题
选择题
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
答案
答案：C
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。