What Does Einstein's Energy Equation (E = Mc²)say About the Energy

What does Einstein's energy equation (E = mc²) say about the energy that is derived from nuclear fission reactions?

A) The energy released is due to the missing mass of the products compared to the mass of the starting materials.
B) The energy is proportional to the change in mass of the nucleus undergoing fission.
C) The energy is derived from the light that is emitted when the atom splits.
D) The energy equation does not apply towards fission, only fusion.
E) none of the above