Answer the following question given this paragraph: 

Energy also constantly changes back and forth between kinetic and potential energy. Kinetic energy is the energy of movement. For example, a ball falling through the air has kinetic energy because it is moving ( Figure below ). The random motion of molecules is due to kinetic energy, and the driving force behind diffusion.


Q: Energy constantly changes back and forth between kinetic and what type of energy?

 Choices:

- practical

- physical

- mechanical

- potential

A:
potential
