问题补充:
Marymy 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:
A. has received
B. ought to have received
(答案→)C. couldn’t have received
D. shouldn’t have received
解析:注意单词otherwise引导虚拟语气。