What Limits the Formation of Giant Stars of Extremely Large

What limits the formation of giant stars of extremely large sizes?

A) Fusion pressures get larger as the size of the star grows,eventually blowing the star into smaller pieces.
B) Heavy elements in the core exert an outward pressure,preventing the formation of a large core.
C) Gas pressure from the outer layers of the star blow the star apart.
D) The core collapses suddenly,causing an explosion before the core can form.