Answer:
option A
Explanation:
In a completely elastic collision, the total kinetic energy is maintained and doesn't change.
Although in a very short time the kinetic energy transforms into potential energy and then again it changes to kinetic energy.
On the other hand, in any collision(elastic or inelastic) the total momentum remains fixed.
The elastic collision from the given option is collision between two billiard balls.
hence, the correct answer is option A
