Answer:
a). whenever the ball is at it's highest on either side (it stops, so kinetic energy is 0)
b). whenever the ball is at the bottom (A) - it cannot go lower, so potential energy is 0.
c). whenever the ball accelerates, so when it's going down from either side before reaching A (at that point it's going up and thus slowing down).
d). whenever the ball is ascending, so when it's goind up from A to either side
Step-by-step explanation:
Kinetic energy is based on velocity
mass is constant, so we need to find a point where v = 0 to solve a), and points where v is increasing to solve b).
Potential energy is based on height vs "the bottom" (here, the minimum altitude is "the bottom").
mass and gravitational acceleration are constant, so we need to find a point where h = 0 to solve b) and the points where h is increasing to solve d).