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 a heat treatment process performed after hardening. By reheating the metal to a temperature below the critical range, internal stresses are relieved and the crystalline structure is stabilized. This process is essential for reducing the extreme hardness and brittleness induced by the initial quenching phase.