When the separation between two charges is increased, the electric potential energy of the charges:

If a positive charge is shifted from a low-potential region to a high-potential region, the electric potential energy:

Consider the situation of the figure. The work done in taking a point charge from \(\mathrm{P}\) to \(\mathrm{A}\) is \(W_{\mathrm{A}}\) , from \(\mathrm{P}\) to \(\mathrm{B}\) is \(W_{\mathrm{B}}\) and from \(\mathrm{P}\) to \(\mathrm{C}\) is \(W_{\mathrm{C}}\). Then:

Which of the following quantities do not depend on the choice of zero potential or zero potential energy?

(a) potential at a point
(b) potential difference between two points
(c) potential energy of a two-charge system
(d) change in potential energy of a two-charge system.
Choose the correct option: 
1. (a) only 
2. (b), (c) 
3. (b), (d) 
4. (a), (d)