Question

how do ligaments help the skeletal system do its job?
over time, ligaments become harder and turn into bone.
ligaments cover and protect bones from the outside.
ligaments move blood between bones.
ligaments connect bones to other bones.

Explanation:

Ligaments are fibrous connective tissues. Their main function in the skeletal system is to connect bones to other bones. Tendons connect muscles to bones. Bones are covered by periosteum (not ligaments). Ligaments do not turn into bone over time in a normal physiological process. And ligaments have no role in moving blood between bones.

Answer:

Ligaments connect bones to other bones.