(2013·四川，5)—Why are your eyes so red？You have slept well last night.
—Yeah，I stayed up late writing a report.
A. can't
B. mustn't
C. needn't
D. won't
网友回答
(答案→)A. can't
B. mustn't
C. needn't
D. won't
解析：
考查情态动词。根据语境“眼睛那么红，昨晚不可能睡得很好”可知，此处考查情态动词can的否定式can't表推测，意为“不可能”。can't have done表示对过去的推测，意为“过去不可能……”。故选A。