Explanation:
(A) Electric field for the parallel plate capacitor is given by :
It is clear that the electric field does not depend on the separation of the plates.
(B) The relation between the electric field and the electric potential is given by :
d is the separation between plates. So, if the separation of the plates is increased, the potential difference increases.
(C) The capacitance of the parallel plate capacitor is given by :
So, the capacitance decreases when the separation of the plates is increased.
(D) The energy stored in the capacitor is given by :
So, the energy stored in the capacitor is increased when the separation of the plates is increased.