When a person breathes, the nose and mouth take in oxygen-rich air, and they expel oxygen-poor air. Which statement explains the change in
oxygen concentration of the inspired air?
A The oxygen concentration decreases gradually as it passes through all organs of the respiratory system,
CB. The oxygen concentration decreases gradually as it passes through all the airways of the lungs,
OC. The oxygen concentration decreases quickly in the nose and mouth, and then remains constant as it passes through other organs of
the respiratory system,
CD. The oxygen concentration decreases only when the air reaches the alveoli, which are the terminal branches of the respiratory system,