∆V represents the voltage difference between any two equipotential surfaces. This value will always remain constant. Then the electric field between the surfaces will depend only on r i.e. the distance between them

Thus, the distance between equipotential surfaces will be smaller wherever there is a strong electric field. Thus, option (a) is correct. As the electric field is strong near the sharp edges of the conductor and near regions of large charge densities, thus, option (b) and (c) are also correct.