When the batter hit the foul ball, the baseball moved upward to a delighted fan in the top deck.
A. KE increases and PE increases.
B> KE increases and PE decreases.
C. KE decreases and PE increases.
D. KE decreases and PE decreases.

B) Kinetic energy increases, potential energy decreases

Explanation:

In a given system, when a body is at rest, v =0m/s, the kinetic energy is at zero while the potential energy is at maximum. However, when a body is in motion with a velocity = v, the potential energy is at zero while the kinetic energy is at maximum.

Before this happen, the a body at rest (P.E = max) is set on motion, the kinetic energy gradually increases till it converts all the potential energy in the system to kinetic energy and then reverses back when the body goes to rest again.

In this case, before the batter hits the ball, the kinetic energy was at zero while the potential energy was at maximum. However, when he hits the ball and sets it into motion with a velocity V, the potential energy converts to kinetic energy and moves the ball with that energy till it has expanded it and comes to rest.

Potential Energy → Kinetic Energy → Potential Energy.

That's how the system keeps changing.