When you bring two negatively charged balloons close to each other, they will repel each other due to the like charges. According to Coulomb's Law, the electrostatic force between two charged objects increases as they come closer together. Therefore, as the distance between the two negatively charged balloons decreases, the electrostatic force will increase, and they will continue to repel each other.
So, the correct statement would be:
"The amount of the electrostatic force between the balloons will increase, and they will repel each other."