Question

—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

Answer 1

C

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。