What is exchanged in the alveoli of the lungs?

In the alveoli of the lungs, the primary function is gas exchange, specifically the exchange of oxygen and carbon dioxide. Alveoli are tiny air sacs surrounded by capillaries, where the process of respiration occurs. When we inhale, oxygen from the air enters the alveoli and diffuses across the alveolar membrane into the blood in the capillaries. Simultaneously, carbon dioxide, a waste product produced by the body's metabolism, is transferred from the blood into the alveoli to be exhaled. This efficient exchange is crucial for maintaining the body's oxygen supply and removing carbon dioxide, thus playing a vital role in cellular respiration and overall physiological homeostasis.

The other options mention substances that are not directly involved in the gas exchange process in the alveoli.