单选题 They reported the traffic accident to the policeman who was ______ for the night.
A. on duty B. on time C. on the sport D. on watch

【正确答案】 A
【答案解析】[考点] 短语辨异。on duty值班、值勤；on time准时；没有on the sport这种搭配；on watch守望。故选A。