(2013·安徽安庆二模)—She looks very happy. She have passed the exam.
—I guess so. It's not difficult after all.
A. should
B. must
C. could
D. might
网友回答
A. should
(答案→)B. must
C. could
D. might
解析：选B 考查情态动词。句意：“她看上去很开心。她一定是通过了考试。”“我想是吧。毕竟考试不难。”四个备选项都可以用来表示推测，must语气最强，然后是should, could, might语气最弱。根据语境，说话人推测她通过考试是有一定的理由的，即她看起来很开心，因此推测时很有把握，故用must。