What Inevitably Forces a Star Like the Sun to Evolve

What inevitably forces a star like the Sun to evolve away from being a main sequence star?

A) The core begins fusing iron.
B) The star uses up all its supply of hydrogen.
C) The carbon detonation explodes it as a type I supernova.
D) Helium builds up in the core, while the hydrogen burning shell expands.
E) The core loses all its neutrinos, so all fusion ceases.