Questions: What gives a nail its hardness? - Calcium - Keratin - Collagen - Melanin

The answer is the second one (Keratin): Keratin is a fibrous protein that gives nails their hardness and strength.

Explanation for each option:

• Calcium: While calcium is important for bone health and strength, it is not the primary component that gives nails their hardness. Nails are primarily composed of keratin.

• Keratin: This is the correct answer. Keratin is a tough, fibrous protein that forms the main structural component of nails, providing them with hardness and resilience.

• Collagen: Collagen is a protein that provides structure and elasticity to skin and connective tissues, but it is not the main component of nails.

• Melanin: Melanin is a pigment responsible for skin, hair, and eye color. It does not contribute to the hardness of nails.

In summary, keratin is the protein responsible for the hardness of nails.