——Tom is never late for work. Why is he absent today?
—— Something to him.
A. must have happened
B. can have happened
C. must happen
D. can happen
网友回答
(答案→)A. must have happened
B. can have happened
C. must happen
D. can happen
解析：考查must表推测，must+have done表示对过去事情肯定的推测。句意：汤姆工作从来没迟到过，为什么他今天没来？他一定出什么事了。故选A。