问题
选择题
The ambulance was just arriving, for a worker, who ______ the window on the second floor, fell off the window.
A．had been repairing
B．was repairing
C．has been repairing
D．would be repairing
答案
答案：A
考查时态。根据句意可知，工人修理窗户发生在掉落下来之前，即过去的过去，过去完成时