The sun will evolve away from the main sequence when
a) its core begins fusing iron
b) its supply of hydrogen
c) the carbon core detonates, and it explodes as a type I supernova
d) helium builds up in the core, while the hydrogen- burning shell expands
e) the core loses all of its neutrinos, so all fusion cease
Answer: d) helium builds up in the core, while the hydrogen- burning shell expands