Question

multiple select question
select all that apply
select all the unique structures made of keratin that are found in mammals.
hooves
teeth
nails
hair
mammary glands

Explanation:

Keratin is a fibrous structural protein. Hooves, nails, and hair are made of keratin. Teeth are mainly made of dentin and enamel (not keratin). Mammary glands are glandular structures (not made of keratin).

Answer:

hooves, nails, hair