问题补充:
—I called you at 9 last night,but no one answered.
—Sorry,I sleeping.I went to bed very early.
A. need have been
B. would have been
C. must have been
D. should have been
答案:
A. need have been
B. would have been
C. must have been
D. should have been
解析:C
解析根据答语中的“I went to bed very early”可知,此处为肯定推测,用must,表示问话人打电话时,答话人一定正在睡觉。must have done表示过去肯定做了某事。