The total amount of energy in the universe never changes, but the availability of each different type of energy to do work can change tremendously. What best explains this change in available energy?

Question

A. Energy can only be transferred as heat.

B. Energy is always converted with 100 percent efficiency.

C. Energy can only be created through nuclear reactions.

D. Energy is regularly changing from one form into another.

Answer 1

The best explanation for the change in available energy is:

D. Energy is regularly changing from one form into another.

This statement highlights that energy can transform from one type to another (e.g., kinetic energy to potential energy, thermal energy to mechanical energy, etc.), which affects its availability for doing work. Other options either misrepresent energy transfer processes or the nature of energy efficiency.