Final answer:
The exchange of oxygen and carbon dioxide takes place in the alveoli, which are small air sacs surrounded by capillaries that facilitate pulmonary gas exchange. So, the correct answer is the second option.
Step-by-step explanation:
The actual exchange of oxygen and carbon dioxide occurs in the alveoli. These are small sac-like structures located at the end of the alveolar ducts and are attached to the respiratory bronchioles. Each alveolar sac contains numerous alveoli, which are covered by a network of thin-walled pulmonary capillaries.
This close proximity ensures that as air enters the alveoli, oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood back into the alveoli. The alveoli are essential for the pulmonary gas exchange, which is vital for respiration.
So, the correct answer is the second option.