— I'm sorry. I _____ at you the other day.

— Forget it. I was a bit out of control myself. [ ]

A. shouldn't shout

B. shouldn't have shouted

C. mustn't shout

D. mustn't have shouted

如图，A、B两点所在的圆半径分别为r₁和r₂，这两个圆为同心圆，圆心处有一带正电为+Q的点电荷，内外圆间的电势差为U．一电子仅在电场力作用下由A运动到B，电子经过B点时速度为v．若电子质量为m，带电量为e．求：

（1）电子经过B点时的加速度大小．

（2）电子在A点时的速度大小v₀．