Question

multiple - choice question
what occurs at the blood - gas barrier?
carbon dioxide moves out of the blood and into the air, which is exhaled. oxygen in the air that was inhaled moves into the blood.
oxygen moves out of the blood and into the air, which is exhaled. carbon dioxide in the air that was inhaled moves into the blood.
both oxygen and carbon dioxide move out of the blood and are exhaled.

Explanation:

Gas - exchange occurs at the blood - gas barrier. Oxygen diffuses from the inhaled air into the blood, while carbon dioxide diffuses from the blood into the air to be exhaled. This is based on the principles of concentration gradients in the respiratory system.

Answer:

Carbon dioxide moves out of the blood and into the air, which is exhaled. Oxygen in the air that was inhaled moves into the blood.