Kidneys help in the maintenance of acid-base balance because

• A

  the renal tubules reabsorb nearly 99% of the filtrate

• B

  tubular cells secrete H⁺ into the filtrate

• C

  DCT is capable of selective secretion of K⁺ into the filtrate

• D

  kidneys have built-in mechanisms for the regulation of glomerular filtration rate