Question

这个题目选哪项?为什么?

all the flights ＿ because of the snowstorm，we had to take the train instead.
a. had been canceled b.having been canceled

Answer 1

b，因为后半句we had to take the train instead是主句，有明显的谓语动词had，所以前句不能有谓语动词，a中的had不能选。这里没有考用什么时态，因为主句是一般过去式，而航班取消一定是发生在搭火车前的，是过去的过去，所以要用过去完成时，b符合这两项，故选b
求采纳~

Answer 2

选B
we had to take the train instead是主语

那么all the flights ＿ because of the snowstorm只能做状语

因此用having been canceled

Answer 3

A，过去完成时选a

Answer 4

选B 考的是非谓语动词 非谓语动词发生在谓语动词之前