33. Which of the following statements about human excretion is correct?
(A) The nephron is the structural unit of the kidney, composed of Bowman's capsule, the renal tubule, the glomerulus, and the collecting duct.
(B) Antidiuretic hormone (ADH) increases urine volume by promoting sodium excretion in the collecting duct.
(C) The filtrate that passes from the glomerulus into Bowman's capsule consists entirely of waste products with no useful substances.
(D) The primary function of the renal tubule is reabsorption; it plays no role in the secretion of waste substances into the filtrate.
(E) Kidney function is regulated by secretions from the parathyroid glands, the posterior pituitary gland, and the adrenal glands.