Which of the following is not a function of locomotion?

Study the following sentences:
$I.$ The accumulation of pyruvic acid in the muscle causes fatigue.
$II.$ $ATP$ is resynthesized in the muscle by the phosphorylation of $ADP$ by a phosphogen.
$III.$ Cori cycle involves muscles and liver.
$IV.$ The phosphogen in the vertebrate muscle is arginine phosphate.
The correct set of statements regarding muscle contraction is:

Which of the following is not a function of the skeletal system?

Analogy type questions:
$(1)$ Carpals : $8$ :: Tarsals : ...........
$(2)$ Cartilaginous joints : Between vertebrae of the vertebral column :: Hinge joint : ...........

Which is not the function of the endoskeleton?

What is the skeletal system? Explain.