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

Energy is always converted with 100 percent efficiency.
Energy is regularly changing from one form into another.
Energy can be transferred as heat.
Energy can only be created through nuclear reactions.

Answer 1

The statement that best explains the change in available energy is:

Energy is regularly changing from one form into another.

This reflects the principle that energy can transform between different types (kinetic, potential, thermal, chemical, etc.), and these transformations affect how available that energy is for doing work. The availability of energy to do work can decrease during these conversions due to processes such as energy dissipation as heat.