题目

汽车在平直公路上以速度v0匀速行驶，发动机功率为P。快进入闹市区时，司机减小了油门，使汽车的功率立即减小一半并保持该功率继续行驶。如图四个图象中，哪个图象正确表示了从司机减小油门开始，汽车的速度与时间的关系(     )  答案：C解析:略  Still many Senior Three students haven't realized reading English newspapers _______of great help to their English study. A. is                B. are               C. have been          D. had heen