Final answer:
The dent in a balloon does not remain after pushing it due to 'elastic rebound', which allows the balloon to return to its original shape once the deforming force is removed.
Step-by-step explanation:
When you push your finger into a balloon and then remove it, the dent does not remain because of elastic rebound. The balloon's material has elasticity, which means it has the ability to return to its original shape after the forces causing the deformation are removed. This behavior is governed by Hooke's Law, which states that for small deformations, the size of the deformation is proportional to the force applied, and the object will return to its original shape when the force is removed. Therefore, the correct answer to why the dent in the balloon doesn't remain is A) Elastic rebound.