Which type of energy increases as its temperature increases?

The correct answer is thermal energy. As temperature increases, the thermal energy of a substance also increases. This is because thermal energy is the energy associated with the random motion of molecules within a substance. When a substance is heated, its molecules gain energy, causing them to move faster and thereby increasing the overall thermal energy of the substance.

In contrast, kinetic energy refers to the energy of motion, which can also increase with temperature in the context of molecular or atomic movement but is not fundamentally defined by temperature alone. Potential energy involves the position or configuration of objects and does not inherently change with temperature. Mechanical energy encompasses both kinetic and potential energy in physical systems but also does not directly correlate with temperature changes in the same way that thermal energy does. Therefore, thermal energy is uniquely tied to temperature increases and is the best fit for this question.