Final answer:
As an object's height above ground increases, its gravitational potential energy increases. This energy is due to its elevated position in a gravitational field, and it increases at the cost of kinetic energy, which is the energy of motion. Option number d is correct.
Step-by-step explanation:
As the height of an object above ground increases, so does its gravitational potential energy. This type of potential energy is the energy an object possesses due to its position in a gravitational field. The Law of Conservation of Mechanical Energy states that in the absence of non-conservative forces such as friction or air resistance, the total mechanical energy of an object (the sum of its kinetic and potential energy) remains constant. As an object rises, its kinetic energy, which is the energy of motion, is converted to gravitational potential energy.
Therefore, if an object like a roller coaster car is at the top of a hill, it has a maximum amount of gravitational potential energy. When an object falls, its potential energy decreases while its kinetic energy increases due to accelerating motion. However, when an object ascends, the process reverses: the object's kinetic energy is converted into potential energy, leading to a decrease in speed.