Answer:
Only gravity acts on B but there is an additional residual force from the hand on A.
Explanation:
All bodies are constantly under the effect of gravity. Gravity is what gives us weight here on earth. Gravity acts downwards, and helps to decrease the deceleration of a body moving up and accelerating a body that travels downwards. For the ball A, traveling upwards, the upwards movement is due to the force on it impacted on it from the hand. As A tries to go up, gravity tries to decelerate it until it will come to a stop and then fall downwards under gravity. For body B, descending down means that only gravity forces acts on it at that point, if we ignore buoyant forces and air resistance. And B accelerates as it falls down towards the juggler.