题目：
— She looks rather upset. She the exam.
— I guess so. It’s very difficult after all.
A．must have failed
B．can fail
C．would have failed
D．should fail
答案：
A
题目分析：考查情态动词。句意 她看起来相当沮丧，肯定是考试不及格。我猜是，比较考试太难了。根据上文提到 She looks rather upset 现在看起来沮丧，下文表示对过去的肯定推测must have done ,所以选A项。
考点 : 考查情态动词
