The correct explanation is:
The force of his hand pushes up on the apple with equal magnitude to the force of gravity, which pulls down on the apple. The two forces are balanced, so the apple doesn't fall.
When the forces acting on an object are balanced, it means that the upward force (from the boy's hand) is equal to the downward force (due to gravity). In this case, since the forces are balanced, the apple remains stationary and does not fall. If the upward force were greater than the downward force, the apple would move up; if the downward force were greater, the apple would fall.