—I wonder why Susan looks worried today. —I’m not sure but she a small accident driving h

问题补充：

—I wonder why Susan looks worried today.

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

A. could have

B. might have

C. might have had

D. must have had

答案：

A. could have

B. might have

(答案→)C. might have had

D. must have had

解析：句意为：----我想知道，Susan今天为什么看上去很忧虑呢？----我也不清楚，但是他可能遇到了一点儿小车祸。 由后面的不太确定，可知应为might, 因为他看上去忧虑，所以事情应该发生了，故应为might have done.答案应为C。