All flights ______ because of the snowstorm, many passengers cou

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】：该题考查独立主格的用法。本题中逗号之前的内容作状语，前后没有连词连接，因此要用非谓语动词的特殊形式—独立主格。