被称为世界桥梁工程中的首创，世界上现存最大的敞肩桥是（ ）。

A．苏州宝带桥

B．赵州桥

C．泉州洛阳桥

D．卢沟桥

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