Just as a Low-Mass Main Sequence Star Runs Out of Fuel

Multiple Choice

Just as a low-mass main sequence star runs out of fuel in its core, it actually becomesbrighter. How is this possible?

A) Helium fusion gives more energy than hydrogen fusion does, based on masses.
B) Its outer envelope is stripped away and we see the brilliant core.
C) The core contracts, raising the temperature and increasing the size of the region of hydrogenshell-burning.
D) It explodes.
E) It immediately starts to fuse helium.