问题补充:
He is an hour late by now.He last night.
A. must stay up
B. should stay up
C. must have stayed up
D. should have stayed up
答案:
A. must stay up
B. should stay up
(答案→)C. must have stayed up
D. should have stayed up
解析:考查虚拟语气。句意:到现在他已经迟了一个小时。他昨晚肯定熬夜了。“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。