Answer:
External respiration: CO2 diffuses into the blood
Step-by-step explanation:
External respiration is also called the pulmonary gas exchange. It refers to the diffusion of O2 from the air in the alveoli of the lungs to blood in pulmonary capillaries and diffusion of CO2 in the opposite direction from the capillary blood into the alveolar air. External respiration in the lungs is responsible for oxygenation of deoxygenated blood coming from the right side of the heart. The oxygenated blood is then returned to the left side of the heart.