Question

----- Mary looks very upset. She _______ failed to pass the exam.
----- I guess so. It's very difficult after all.
A  must have   B could have   C should have  D might have

Answer 1

A

本题考查情态动词的用法。句意：玛丽看起来很沮丧。她一定没有通过考试。must have done过去一定做过某事。