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:A考查情态动词的用法。句意:“你的眼睛为什么那么红啊?昨晚你不可能睡得很好。”“是的,我熬到很晚写一篇报告。”can have done指过去不可能做……。