Answer
(a) decrease
(b) II
Work Step by Step
(a) We know that when the electron moves, its kinetic energy increases and according to the law of conservation of energy its electric potential energy decreases.
(b) The best explanation is option (II) -- that is, as the electron begins to move, its kinetic energy increases. The increase in kinetic energy is equal to the decrease in the electric potential energy of the system.
