問題詳情：
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
【回答】
A
【解析】
考查時態。根據句意可知，工人修理窗戶發生在掉落下來之前，即過去的過去，過去完成時
知識點：過去完成進行時
題型：選擇題
