题目内容：

the fights ________because of the snowstrom,many passengers could do nothing but take the train.
A.had been canceled B.have been cancled C.were canceled D.having been caneled 为什么选D

优质解答

真正的主句是many passengers could do nothing but take the train.这是一个完整的句子.
中间用逗号隔开了,就表示the fights having been caneled because of the snowstrom不是一个句子,这里相当于一个状语从句.