Question

which best describes thermal energy? it is the difference between internal energies of two or more substances. it is the sum of internal energies of two or more substances. it is the portion of internal energy that can be transferred from one substance to another. it is the portion of potential energy that can be transferred from one substance to another.

Explanation:

Thermal energy is the part of internal energy that can be transferred as heat between substances due to a temperature difference. It's not about the difference or sum of internal energies in general, nor is it related to potential - energy transfer in this context.

Answer:

It is the portion of internal energy that can be transferred from one substance to another.