题目

A、B两物体分别在水平恒力F1和F2的作用下沿水平面运动，先后撤去F1、F2，两物体最终停下，它们的v-t图像如图所示。已知两物体与水平面间的滑动摩擦力大小相等。则下列说法中不正确的是（ ） A.全过程中A、B的平均速度之比为1∶1B.A、B质量之比为2∶1C.F1、F2冲量大小之比为1∶1D.全过程中A、B克服摩擦力做功之比为2∶1Only when class began _____ that he had left his book at home. [     ]A. will he realize B. he did realizeC. did he realizeD. should he realize