高一英语题!麻烦解释一下,谢谢!

Question

22. --- I called you last night, but nobody answered the phone.
--- Sorry, ________.
A. I must be sleep at that moment. B. I must have slept at that moment.
C. I must have been asleep at that moment. D. I must have fallen asleep at that moment.

Answer 1

选C。我不同意一楼的回答。题目中的他没听电话，肯定是因为他睡着了。C和D的区别就是asleep和fall asleep 的不同。
意思都是入睡但fall asleep强调入睡的动作
be asleep 强调睡着的状态
例如：The baby is asleep,don't turn up the radio.
My father was so tired that he fall asleep quickly.
所以选c更好，因为强调他睡着了，而不是D已经在入睡这个动作

Answer 2

D 是我个人认为，由题意应该是在他打打电话给我时我已经睡了。应用过去完成时，且“入睡”用fall asleep。本回答被网友采纳