The Structure of the Deep Interior of a Low-Mass Star

The structure of the deep interior of a low-mass star near the end of its life is a(n)

A) carbon-oxygen core, a shell around the core where helium nuclei are undergoing fusion, and a surrounding shell of hydrogen.
B) inactive hydrogen core and a helium shell undergoing nuclear fusion surrounded by a carbon-oxygen shell.
C) turbulent mixture of hydrogen, helium, carbon, and oxygen in which only helium continues to undergo nuclear fusion.
D) helium core surrounded by a thin hydrogen shell undergoing nuclear fusion with very small concentrations of heavier nuclei.