—He didn’t devote his time to his study，
题型：选择题
问题：
—He didn’t devote his time to his study，did he?
— ．As a result，he failed all the final exams．
A．Yes，he did
B．No，he didn’t
C．Yes，he didn’t
D．No，he did
题型：选择题
| 如图所示，充电后的平行板电容器竖直放置，板间一带正电的绝缘球用绝缘细线悬挂于A板上端，若将小球和细线拉至水平位置，由静止释放后小球将向下摆动直至与A板发生碰撞，此过程细线始终处于伸直状态，则此过程中（ ） A．小球电势能一直增加 B．小球的动能一直增大 C．小球受细线的拉力一直在增大 D．小球运动的向心加速度先增大后减小  |