如图所示，在两平行金属板中央有一个静止的电子（不计重力），当两板间加上下图所示的交变电压后，能使电子有可能做往返运动的是
A．
B．
C．
D．
ABC
Mr.Hunter managed to his neglect of his duty on the basis of his poor health. [ ]
A.remember
B.forget
C.reject
D.justify
轨道面
