As a graducate in puter science, he to work out the problem.
A. wouldn't have failed
B. can't have failed
C. mustn’t have failed
D. might not have failed
网友回答
A. wouldn't have failed
(答案→)B. can't have failed
C. mustn’t have failed
D. might not have failed
解析：can’t/couldn't have done表示对过去发生的事情的否定推测。