The Helium Flash Occurs in a 2-Solar-Mass Star When

The helium flash occurs in a 2-solar-mass star when

A) the core heats up from helium fusion and the gas does not expand to cool down and stabilize the temperature because the gas properties are controlled by degenerate electrons.
B) convection within the star carries helium to the surface, where it shows its own characteristic spectrum for the first time.
C) hydrogen fusion ceases abruptly, leaving only the fusion of helium to generate energy.
D) the core temperature becomes sufficiently high for helium fusion for the first time.