Why Does the Luminosity of a High-Mass Star Remain Nearly

Why does the luminosity of a high-mass star remain nearly constant as the star burns elements heavier than helium in its core, even though it is producing millions of times more
Energy per second than it did on the main sequence?

A) Most of the energy is trapped in the core, increasing the core's temperature.
B) All of the extra energy goes into heating the shells of fusion surrounding the core.
C) Most of the energy is absorbed by the outer layers of the star, increasing the star's radius but leaving its luminosity unchanged.
D) Most of the energy is carried out of the star by escaping neutrinos.
E) All of the energy goes into breaking apart light elements such as helium and carbon.