问题
选择题
— Tom is never late for work. Why is he absent today ?
— Something _______ to him.
A．must happen
B．should have happened
C．could have happened
D．must have happened
答案
D
must have done表示对过去事情的肯定推断，意为：过去一定做了某事。A表示对现在或示来事情的肯定推敲；B意为：本应该发生；C意为：可能已经发生，口气不太肯定，由于前一句意为：汤姆上班从未迟到过，而判断他今天缺席一定是因为出了什么事了。