Which statement best describes the nature of temperature?

Temperature is fundamentally a measure of the average kinetic energy of the molecules that make up a substance. As the temperature increases, the molecules move more vigorously, which correlates directly with their kinetic energy; hence, higher temperatures indicate greater molecular motion. This definition holds true not only for gases but also for liquids and solids, as all matter is made up of particles that are in constant motion at various energy levels depending on the temperature.

The other choices do not accurately describe the nature of temperature. For example, mass describes the amount of matter in a substance rather than the energy associated with its molecular motion. Similarly, while the chemical composition may influence properties of a substance, it does not directly relate to its temperature. Lastly, the link between temperature and gas pressure is more specific to the behavior of gases under specific conditions rather than a general description of temperature itself.