As an object falls from a height, there are various factors that change. However, one of them remains constant, and that is its acceleration.

Option 1: Acceleration. Acceleration is the rate at which the velocity of an object changes with time. In this case, as the object falls towards the floor, its velocity increases, which means that its acceleration remains constant. This is due to the constant force of gravity acting on the object.

Option 2: Momentum. Momentum is the product of an object`s mass and velocity. As the object falls towards the floor, its velocity increases, which means that its momentum also increases. Therefore, the momentum of the object is not constant.

Option 3: Kinetic Energy. Kinetic energy is the energy possessed by an object due to its motion. As the object falls towards the floor, its velocity increases, and as a result, its kinetic energy also increases. Therefore, the kinetic energy of the object is not constant.

Option 4: Potential Energy. Potential energy is the energy possessed by an object due to its position or height above the ground. As the object falls towards the floor, its height decreases, and therefore, its potential energy decreases. Therefore, the potential energy of the object is not constant.