I made a phone call to you without an answer last night,you _____ out at that moment.

问题描述:

I made a phone call to you without an answer last night,you _____ out at that moment.
A) might be B) must have been C) must be D) were

must be一定;一定要;肯定是
-might be: 可能是可能是
must have been一定(对过去事实肯定的推测)
were 是
因此只能是B,表示对昨天他不在的这个事实的推测.