ANS:D - Dissolved elements (except cobalt)

Coarse grains of austenite decrease the hardenability in steel. When steel is being heat-treated for hardening, the transformation of austenite to martensite (the hardest phase of steel) depends on the rate at which it is cooled (quenched). Coarse grains of austenite provide fewer nucleation sites for the martensitic transformation, leading to less uniform and less effective hardening. Therefore, coarse grains decrease the hardenability of steel.