题目

 （2013山东省名校质检）一辆质量为m的汽车在发动机牵引力F的作用下，沿水平方向运动。在t0时刻关闭发动机，其运动的v-t图象如图所示。已知汽车行驶过程中所受的阻力是汽车重量的k倍，则（     ）A.加速过程与减速过程的平均速度比为1∶2B.加速过程与减速过程的位移大小之比为1∶2C.汽车牵引力F与所受阻力大小比为3∶1D.汽车牵引力F做的功为(1)  As Polly o____________(86) the passengers on the train, she s______________(87) that she was being watched by a tall man in a dark coat. At last the train arrived at Green Park station. While the rest of the passengers were getting out, she g______________(88) at the faces around her. The tall man was nowhere to be seen.