Concept:Nails are primarily made of a fibrous structural protein that provides strength and protection.
Explanation:Keratin is the key structural protein present in nails, hair, and the outermost layer of skin.
It is a scleroprotein rich in the amino acid cysteine.
Disulfide bonds formed between cysteine residues impart hardness and water resistance to nails.
This fibrous protein protects the fingertips from mechanical injury.
Keratin is also a major component of claws, horns, and feathers in animals.
Legumelin is a seed protein found in plants, not in nails.
Myosin is responsible for muscle contraction.
Insulin is an endocrine hormone that controls blood sugar levels.
These proteins do not form nail tissue.
Hence, keratin is the correct protein found in nails.
Answer:Option B. Keratin