The skeletal system serves all of the following functions except:
a. bone marrow produces red and white blood cells which carry oxygen through the blood and fight diseases.
b. the skeleton gives the human body its support, shape, and form.
c. the skeletal system to protect vital organs.
d. the skeletal system aids in the production of hormones that signal muscle and hair growth.

The question says, 'the skeletal system serves all the following functions except The correct option is D. This is because all the other options given are functions of the skeletal system. The skeletal system does not participate in the production of hormone that signal muscle and hair growth. It is testosterone hormone that regulate hair growth and the skeletal system is not involved in its production.