The correct answer is option 3: Acceleration. When throwing a ball upward, the acceleration remains constant.

To understand why this is the case, we need to consider the forces acting on the ball. When the ball is thrown upward, there are two main forces at play: gravity pulling the ball downward and the force exerted by the person throwing the ball. These forces affect the ball`s motion.

Initially, when the ball is thrown upward, the force exerted by the person throwing the ball is greater than the force of gravity. This causes the ball to accelerate upwards. However, as the ball moves higher, the force of gravity becomes stronger and eventually surpasses the force exerted by the person throwing the ball.

At this point, the ball starts to decelerate and eventually starts moving downward. Throughout this motion, the acceleration remains constant because the force of gravity is constant. The acceleration due to gravity near the surface of the Earth is approximately 9.8 meters per second squared (m/s^2).

Therefore, while throwing a ball upward, the acceleration remains constant, regardless of the other factors such as displacement, kinetic energy, or velocity.