4. Which of the following statements about excretory system is NOT TRUE?
(A) Nephron is the functional unit of kidney
(B) The nephron consists of a single long tubule and a ball of capillaries called the glomerulus. Filtration occurs as blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman's capsule
(C) Filtration of small molecules s passes through three regions of the nephron: the proximal tubule, the loop of Henle, and the distal tubule, which are all permeable to salt but not to water
(D) The controlled movement of ions (such as ) in the proximal and distal tubules contributes to constant pH in the body fluid