问题
选择题
Mary was caught in a traffic jam and by the time she arrived at the airport her father’s plane_______.
A．took off
B．had already taken off
C．was take off
D．had already been taken off
答案
B
by the time与she arrived这一过去的动作连用，表示到过去那时为止已经完成的动作，用过去完成时。take off指“起飞”，没有被动语态。