问题补充:
It is when the plane that you’d better find out at the booking office.
A. would take off
B. had taken off
C. was taking off
D. is taking off
答案:
A. would take off
B. had taken off
C. was taking off
(答案→)D. is taking off
解析:注意题干为强调句型。take off用进行时态表示将来。