All flights（）because of the snowstorm, many passengers could do nothing but take the train.
A、
were canceled
B、
have been canceled
C、
had been canceled
D、
having been canceled
【正确答案】：D
【题目解析】：
独立主格结构，前一半是原因状语，由于所有的航班都被取消了，该动作发生在前，许多乘客只得坐火车了，该动作发生在后。前半句主语是航班，后半句是乘客，主语不一致，因此用独立主格结构。
