In my opinion, all Mr Li ______ good to his students in his class at present. He is very strict with them in their studies.

A．does does does

B．does does do

C．does do did

D．did do does

空间有p、q两个点电荷相距r且仅在相互间的库仑力作用下从静止开始运动，开始时p的加速度为a，q的加速度为4a，经过一段时间后，q的加速度为a，速度达到v，则这时p的加速度和p、q两个点电荷相互间的距离的大小为（　　）

A．4a、4r

B．a、

C．

D．