—Why does Mary look so worried today?—I’m not sure but she a small accident driving here

问题补充：

—Why does Mary look so worried today?

—I’m not sure, but she a small accident driving here.

A. must have

B. might have

C. must have had

D. might have had

答案：

A. must have

B. might have

C. must have had

(答案→)D. might have had

解析：考察情态动词用法。“情态动词+have done”表示对过去情况的虚拟或者推测；“情态动词+动词原形”表示对现在情况的虚拟或者推测。句义：—为什么Mary今天看起来很担忧啊？—我不清楚，也许是在开车来的时候，出了点小事故吧！根据句义可知是对过去发生的事情的推测。Must have done一定做了某事，表示对过去所发生的事情有把握的肯定推测。Might have done也许做了某事，表示没有把握的推测。故D正确。