—Mary’s score on the test is the highest in her class.
—Really? She have studied very hard.
A. may
B. ought to
C. must
D. should
网友回答
A. may
B. ought to
(答案→)C. must
D. should
解析：考查情态动词表示推测。Must have done一定做了某事；B=D，所以排除。May have done也许做了某事；句意：—Mary的考试分数是班级里最高的。—真的吗？她肯定学习的非常认真。