Question

keratin is a hard protein that is found in layers on __________ and __________. toenails teeth fingernails hair

Explanation:

Keratin is a structural protein found in epithelial tissues. Toenails, fingernails, and hair are composed of keratin, while teeth are not (made of enamel/dentin). The question requires two answers from the correct options.

Answer:

C. fingernails, D. hair