Correct option is C
In the normalising process, the workpiece is heated above its critical temperature and then allowed to cool naturally in still air. This cooling rate is faster than furnace cooling (used in annealing) but slower than quenching in water or oil.
This controlled cooling refines the grain structure, producing a uniform and fine microstructure, which improves mechanical properties like strength and toughness. Rapid cooling (quenching) would produce harder but more brittle structures like martensite, which is not desired in normalising.
