Which of the following is an accurate statement about myelin and myelinization?

Which of the following is an accurate statement about myelin and myelinization?

a) Myelin slows message transmission between neurons; the reduction of myelin reflects increasing brain maturation.

b) When examining brain development between conception and adolescence, maturity is positively correlated with myelinization.

c) Myelinization occurs in the areas that control the legs before it occurs in areas that control the arms.

 d) Myelinization occurs before cell migration occurs.