Question

14 hair, nails, and the outer layer of the skin are made mostly of a tough waterproof protein called: a carotene b collagen c keratin d elastin

Explanation:

Keratin is a tough, fibrous protein that forms the structural framework of hair, nails, and the outer - layer of the skin, providing waterproofing and strength. Carotene is a pigment, collagen is mainly in connective tissues like tendons and ligaments, and elastin provides elasticity in tissues like skin and blood vessels but is not the main protein in hair, nails, and the outer - skin layer.

Answer:

C. keratin