----- 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

劳动纪律整顿的对象或内容主要有（）

A.长期旷工人员

B.长期请病假人员

C.未及时进行工伤认定和劳动能力鉴定的人员

D.挂职领薪人员

E.冒名顶替人员

F.劳动纪律松懈，迟到早退人员