Answer:
The force of repulsion between the two balls will increase
Step-by-step explanation:
The electrostatic force between two charged objects is given by

where
k is the Coulomb's constant
q1 and q2 are the charges of the two objects
r is the distance between the centres of the two objects
We see that the magnitude of the force is directly proportional to the charges on the two objects. in this problem, we have two positively charged balls (so, there is a force of repulsion between them, since like charges repel each other and unlike charges attract each other), and the positive charge in one of them is slowly increased: this means that either
or
in the formula is increasing, and so the magnitude of the force is increasing.