如图所示，水平固定的带电小圆盘A，取盘中心O点的电势为零，从盘心O处释放一质量为m，带电量为+q的小球，由于电场的作用，小球竖直上升的最大高度可达盘中心竖直线上的C点，且OC=h，又知道小球通过竖直线上B点时的速度最大且为v_m，由此可以确定

A．B点的场强和C点的场强

B．C点的场强和B点的电势

C．B点的场强和C点的电势

D．B点的电势和C点的电势

动词填空。 用括号中所给动词的适当形式填空，要求语法正确，句意完整。

1. It's hard to believe that Helen can _________ (speak) Japanese so well.

2. Nowadays recorders _________ (use) by English teachers in class.

3. Thanks to their help, we _________ (finish) the work already.

4. Will you ring me up as soon as your mother_________ (get) to Beijing?

5. I _________ (put) up a map on the wall when Mr. Shute came in.

6. Listen. John is practicing _________ (sing) an English song in the room.