—She looks very happy. She have passed the exam.
--I guess so. It’s not difficult after all.
A. should
B. could
C. must
D. might
网友回答
A. should
B. could
(答案→)C. must
D. might
解析：考查虚拟语气。句意：她看起来非常高兴。她肯定是通过了考试。——我猜是这样。这毕竟不太难。“should+have+done”意思是“本来应该做某事，而实际没做；“could+have+done”表示对过去事情的假设，意思是本来能够做某事而没有做；“must+have+done”表示对过去事情的肯定推测，译成“一定做过某事”； “might+have+done”表示对过去已经发生的事情的推测，might与may意思相同，但可能性更小。结合语境可知上文为肯定推测，故选C。