21. Which of following is NOT true? (A)Melatonin regulates functions related to light and to seasons marked by changes in day length. (B)Vitamin D actvation begins in the kidneys and is completed in the liver. (C)Prolactin regulates fat metabolism in birds. (D)Humans require thyroid hormones for the normal function of bone-forming cells. (E)In mammals, melanocyte-stimulating hormone (MSH) functions in hunger and metabolism in addition to coloration.