Correct option is D
Hardness is the property of a material that defines its resistance to deformation, scratching, indentation, and wear. It is an important characteristic in engineering materials, especially for cutting tools, machine parts, and wear-resistant surfaces.
Common methods to measure hardness include:
· Brinell Hardness Test (BHN) → Uses a steel or tungsten carbide ball.
· Rockwell Hardness Test (HRB, HRC) → Uses a steel or diamond cone (for metals).
· Vickers Hardness Test (VHN) → Uses a diamond pyramid.
· Mohs Hardness Test → Ranks materials from 1 (talc) to 10 (diamond).
