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

【正确答案】 D

【答案解析】[解析] 其他三个选项都是谓语动词形式。由于题干用的是逗号并且没有连接词，因此可以判断它不是一个并列句。句中的having been cancelled为现在分词的完成被动形式，连同它的逻辑主语all flights一起构成分词的独立结构，在句中作状语．表示原因。