All flights _________ because of the snowstorm,many passengers could do nothing but take the train.A.had been canceledB.have been canceledC.were canceledD.having been canceled

问题描述:

All flights _________ because of the snowstorm,many passengers could do nothing but take the train.
A.had been canceled
B.have been canceled
C.were canceled
D.having been canceled

因为句中逗号,逗号前不是一个句子,所以直接排除ABC,选D