问题补充：
— Is John coming by train?
— He should, but he not. He likes driving his car.
A. must
B. can
C. need
D. may
答案：
A. must
B. can
C. need
(答案→)D. may
解析：先确定问句为将来时态，因为像come, go, leave, start等等这类趋向动词的进行时表示将来时。这是至关重要的，因为答语是就一将来的动作作出判断的。先排除A项，must not译为“不准”，与文意不合；再排除B项，至少cannot不可分开写；最后排除C项， need not译为“不必”，与文意相左；只有选D项，译为“可能不，不一定”，正好与后文的He likes driving his car相吻合，故应选D项。
