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

考察情态动词用法。Must have done一定做了某事；could have done本可以做某事；should have done sth本应该做某事；might have done也许做某事；结合句意可知A正确。句意：—玛丽看起来很难过。她一定考试没有及格。