题目

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：A 【解析】 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

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