An increase in the temperature of an object means that the thermal energy has increased; option [D]. Temperature is a measure of the average kinetic energy of the molecules within an object. As temperature rises, the molecules move faster, increasing the object’s overall thermal energy. Thermal energy is the total kinetic energy due to the random motion of particles in the object. This increase in thermal energy is not the same as an increase in potential energy, which is related to the position of objects in a field, or mechanical energy, which includes both kinetic and potential energy in a macroscopic system. Therefore, when an object’s temperature increases, its thermal energy increases as well, reflecting the higher kinetic energy of its molecules. Thus, the correct option is [D] Thermal energy has increased.