Answer:
Just as it reaches the top of the bounce.
Step-by-step explanation:
When an object reaches to the maximum height, its kinetic energy is equal to 0. It can be calculated as follows :
Where
m is mass and v is velocity
In this problem, Anita is bouncing a tennis ball on the sidewalk. She drops the ball and then watches it bounce back up.
It means, when it reaches the top of the bounce, Anita's tennis ball have zero kinetic energy. Hence, the correct option is (d).