When hardened metal is heat-treated by a process known as tempering, what metallurgical properties are achieved?

Correct Answer: Option A — decrease in brittleness

Hardened steel is typically too brittle for most mechanical applications. Tempering reduces this brittleness by allowing the internal stresses caused by rapid quenching to relax. While this slightly reduces the overall hardness, it significantly improves the material's toughness and ductility, making it less prone to sudden, catastrophic failure.