All the flights

All the flights ______ because of the snowstorm, we had to take the train instead.

were canceled

had been canceled

having canceled

having been canceled

答案及解析：本题考查非谓语句意：所有的航班因为暴风雪已经取消了,我们决定乘坐火车独立主格结构在句中一般只做状语,且用逗号和句子其他成分隔开，且前后主语不一致，逗号前后两个成分,后部分句首并没有并列连词and/so等,前部分也没有because等,说明这是一个简单句,而逗号前面只是一个状语,而不是一个并列句/复合句。如果是并列句,则句子应该写成：All flights had been canceled because of the snowstorm,so we decided to take the train.如果是复合句,则句子应该写成：Because all flights had been canceled because of the snowstorm,we decided to take the train.由此可以排除使用两句的选项AB,因为它们都是一个句子的谓语结构；而all flights和cancel之间明显是被动关系,而C则也是句子的谓语结构,则它表明all flights和cancel之间为主动关系,排除.D项是语法上的独立主格结构,该结构中的非谓语结构having been canceled的逻辑主语是其前的all flights,并非句子的主语we；它表明all flights和cancel之间为被动关系,且cancel该动作发生在谓语动词decided to...之前.故正确答案为D选项。