Which of the Following Is NOT a Function of the Kidneys

Which of the following is NOT a function of the kidneys

A) to act directly on the interstitial fluid, the fluid that bathes the cells, to maintain constancy in its composition
B) to contribute significantly to long-term regulation of arterial blood pressure by maintaining the proper plasma volume
C) to excrete metabolic waste products
D) to assist in maintaining the proper acid-base balance of the body