Which of the following statements is true?
a) Most humans have one kidney, which regulates water and electrolyte balance, removes nitrogenous wastes from the blood, and eliminates the wastes in the urine.
b) The kidneys regulate water and blood glucose in terrestrial vertebrates.
c) The kidneys are paired organs that remove nitrogenous wastes from the urine. d) The kidneys are paired organs that regulate water and electrolyte balance in terrestrial vertebrates.