The correct answer is: Just after it hits the ground.
The ball has zero kinetic energy at the very top of its bounce. To understand this, we need to consider the definition of kinetic energy. Kinetic energy is the energy possessed by an object due to its motion. In the case of the bouncing tennis ball, when it is at the top of its bounce, it momentarily comes to a stop before changing direction and moving back downwards. At that moment, the ball is momentarily at rest, meaning it has zero velocity. Since kinetic energy depends on both mass and velocity, if the ball has zero velocity, its kinetic energy will also be zero. Therefore, the correct answer is "At the very top of its bounce."
