What Is the MAIN Source of the Energy Radiated by Stars

What is the MAIN source of the energy radiated by stars?

A) Chemical reactions combine hydrogen and helium to produce energy.
B) Protons are destroyed and converted into pure energy as described by Einstein's mass-energy relationship.
C) Less stable nuclei combine to form more stable nuclei with a consequent release of energy.
D) gravitational collapse as described by the Kelvin-Helmholtz contraction