Answer:
It sticks to the wall due to electrostatics.
Step-by-step explanation:
When pam rubs a balloon against his hair, and holds it up against the wall, he is basically adding a surplus of electrons which are negative charges to the surface of the balloon.
This motion would make the wall the more positively charged than the balloon. Therefore, when the two charges come in contact with each other, the balloon will stick to the wall because of the rule in electrostatics that opposite charges attract each other.