问题补充:
He is an hour late by now.He last night.
A. must stay up
B. should stay up
C. should have stayed up
D. must have stayed up
答案:
A. must stay up
B. should stay up
C. should have stayed up
(答案→)D. must have stayed up
解析:考查情态动词表推测。根据last night,可知是指过去的事情,要用情态动词加完成时态,表对过去事实的推测,排除A,B;should have stayed up本应该熬夜而实际没有,must have stayed up表肯定熬夜了。根据他迟到这一事实,可知他昨晚肯定熬夜了,才导致迟到这一事实,所以选D。