The skeletal system is the framework of the human body, comprised of bones, joints, and connective tissue. The integumentary system forms the largest system of the human body and is made up of skin, hair, nails and glands. How do the skeletal and integumentary systems work together to protect the human body?
A. The two systems initiate muscle contractions that protect the human body.

B. The two systems provide a barrier between the outside environment and the internal organs of the body.

C. The two systems initiate an immune response that protects the human body.

D. The two systems deliver signals between the outside environment and brain.