问题
选择题
—Peter looked tired and a little absent-minded in class．
—He _____ too late．
A．may stay up
B．could stay up
C．should have stayed up
D．must have stayed up
答案
答案：D
考查情态动词表推测的用法。must have done 表示对过去事情肯定的推测，句意： 皮特看起来很累在课上有点心不在焉。他一定熬夜熬得太晚了。所以选D。