—Did you look up the time of trains to Shanghai?
—Yes, the earliest train is to leave at 5:30 am.
A. likely
B. about
C. possible
D. due
网友回答
A. likely
B. about
C. possible
(答案→)D. due
解析：be due to do意为“应该…/预期的”；be about to do 不和时间状语连用；possible主语应为it；而likely与句意不合。