Since there is no frictional loss or any other type of resistive loss in this motion of charge from one position of electric field to other position. So here we can say that total mechanical energy of the charge system will remain conserved always
So here we can say that mechanical energy is sum of kinetic energy and electrostatic potential energy which will remains conserved always
So here correct answer will be
A). The sum of the potential energy and the kinetic energy at A is the same as that at B.