All flights ___ because of the heavy snow,we had to take the train.

问题描述:

All flights ___ because of the heavy snow,we had to take the train.
A.were canceled B.had been canceled
C.have been canceled D) having been canceled

A .C 可以先排除.B和D我徘徊了很久,D应该比较正确吧,现在分词作原因状语.主句明显是是在后半句是结果.如果用其他选项应该无法体现出先后时间上的差别吧.有正确答案告诉下.