单选题 ______ the policeman approaching, the driver brought his car to a halt quickly.
A. Saw B. Having seen C. Seen D. Seeing

【正确答案】 D
【答案解析】[解析] 虽然从句表示的动作先发生，但由于是瞬间完成的，而且主句表示反应或行动，不用完成时。