What are the two forms of stored thermal energy?

The correct choice identifies the two forms of stored thermal energy as internal potential energy and internal kinetic energy. Internal potential energy refers to the energy stored within the system due to the position of the particles relative to each other, which can be influenced by forces such as bonds within molecules. Internal kinetic energy, on the other hand, refers to the energy associated with the motion of those particles. The combination of these two forms of energy determines the thermal energy content of a substance, contributing to its temperature, phase, and other thermodynamic properties.

Regarding the other choices, they do not accurately reflect the specific types of stored thermal energy. Kinetic energy and thermal radiation are more related to energy in motion and energy emitted in the form of electromagnetic waves, respectively. Electrical energy and chemical energy are distinct forms of energy that do not specifically address thermal storage. Lastly, mechanical energy and sound energy pertain to motion and vibrational energy, neither of which adequately represent the internal energy components relevant to thermal storage.