Option (a) is incorrect because potential at a point depends on our choice of zero potential. Normally infinity is taken as reference point where potential is assumed to be zero.

If choice of zero potential is changed, then the potential at a point will also change.

Option (b) is correct as difference in potential between the two points doesn’t depend on the choice of zero potential.

Option (c) is incorrect as the potential energy of the two-charge system also depends on the choice of zero potential in order to calculate the potential at the point where the two charges are kept.

Option (d) is correct as the change in potential energy of the two-charge system is independent of our choice of the zero-potential point.

Thus, we conclude that potential difference between two points and change in potential energy of a two-charge system don’t depend on the choice of zero potential point.