问题补充:
I asleep because it took me a long time to realize that the telephone was ringing.
A. could have fallen
B. should have fallen
C. must have fallen
D. mustn’t have fallen
答案:
A. could have fallen
B. should have fallen
(答案→)C. must have fallen
D. mustn’t have fallen
解析:考查虚拟语气。句意;我肯定是睡着了,因为用了很长时间我猜意识到电话铃一直在响。“must+have+done”表示对过去事情的肯定推测,译成“一定做过某事”。故选C。