Reheating a hardened component to a temperature lower than the hardening temperature and then cooling it is known as __________.

Correct Answer: Option D — tempering

Tempering is the metallurgical process of reheating a previously hardened steel component to a specific temperature below the transformation range, followed by controlled cooling. This procedure is essential to reduce the extreme hardness and brittleness induced by quenching, thereby improving the component's ductility and impact resistance for operational service.