问题:
[单选] They happened to__________ for Tianjin when we got there.
A . leave
B . have left
C . leaving
D . had left
正确答案:B
参考解析:happen to后接动词原形,所以先排除C、D,而不定式表示的动作发生于过去,故选B。

问题:
[单选] They happened to__________ for Tianjin when we got there.
A . leave
B . have left
C . leaving
D . had left
正确答案:B
参考解析:happen to后接动词原形,所以先排除C、D,而不定式表示的动作发生于过去,故选B。