In mammals, blood pH must be kept fairly constant (very close to 7.4) in order for these animals to survive. Which two organs play the MOST IMPORTANT role in regulating blood pH in mammals?

Blood pH in mammals is chiefly regulated by the kidneys and lungs. The lungs remove nearly all of the CO2 from the blood, preventing acidosis. Bicarbonate is adjusted by the kidneys to prevent acidosis and alkalosis. Therefore, the correct answer is kidneys and lungs.