Why Is Iron the Heaviest Element Formed in a Star

Why is iron the heaviest element formed in a star prior to the formation of a supernova?

A) The formation of iron in a star starts a cooling process of the star, ending nucleosynthesis.
B) Iron reacts with the hydrogen in stars to cause a violet explosion that leads to a super nova.
C) Iron is the heaviest element that is stable at high temperatures; all others are radioactive.
D) The formation of iron in a star causes a reaction with helium that causes nucleosynthesis to end.
E) When iron is formed in the outer layers of a star, the iron has enough kinetic energy to leave the gravity of the star.