问题补充:
(·四川高考)—Why are your eyes so red? You have slept well last night.
—Yeah, I stayed up late writing a report.
A. can
B. mustn
C. needn
D. won
答案:
(答案→)A. can
B. mustn
C. needn
D. won
解析:选A考查情态动词。句意:“你的眼睛为什么这么红?昨晚你不可能睡好觉。”“是的,我熬夜写一篇报告。”can have done表示对过去事情的推测,表示“不可能做过某事”。