Answer:
Two balloons will repel each other
Step-by-step explanation:
As we know that the basic property of electric charge is as following
1. It two similar charges are placed near to each other then they repel each other and moves apart
2. If two opposite charges are placed near to each other then they attract each other and comes closer to each other.
so here in the above case when two balloons have negative charge then due to similar charges on them the two balloons will repel each other and moves apart from each other