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 often too brittle for practical use, making it susceptible to sudden fracture under impact. Tempering reduces this brittleness by allowing for a slight transformation of the martensitic structure, which increases the material's toughness and ductility while maintaining a significant portion of the original hardness.