Among vertebrate animals, urea A) is made in the kidneys and immediately excreted. B) is added to the air in the lungs to be exhaled, along with carbon dioxide. C) is made in the liver by combining two ammonia molecules with one carbon dioxide. D) is made in the pancreas and added to the intestinal contents, along with bile salts, for excretion. E) is rarely the nitrogenous waste of choice.