题目

 ―What about swimming together with me?―________________________. A. Help yourself                                              B. Go ahead, pleaseC. Me, me                                                      D. Good idea 答案：D   如图所示，将一个小球用细线悬挂起来，让小球在a、b之间来回摆动，c点为小球圆弧轨迹的最低点，则以下说法中正确的是（　　）A．小球由a到c的过程，动能减小，重力势能增大B．小球由c到b的过程，动能减小，重力势能增大C．小球在c点时的重力势能最大D．小球在b点时的动能最大