The correct answer is A) increase the distance between the two charges.
Electric potential energy is the energy that is stored in a system of two or more electrically charged objects due to their position relative to each other. As the distance between the charged objects increases, the electric potential energy of the system decreases. This is because the electrical force between the objects decreases as the distance between them increases. Therefore, by increasing the distance between two positively charged objects, the electric potential energy of the system will decrease.
Decreasing the distance between the two charges (option B) would actually increase the electric potential energy of the system, as the electrical force between the objects would increase. Changing the mass of the objects (options C and D) would not have any effect on the electric potential energy of the system, as electric potential energy depends only on the charges and their separation distance.