What occurs as gases are exchanged in the alveoli?

As gases are exchanged in the alveoli, oxygen from the air that has been inhaled diffuses into the blood while carbon dioxide (CO2) diffuses from the blood into the alveolar space to be exhaled. This process is essential for maintaining the body's oxygenation and getting rid of metabolic waste products.

The correct answer captures a misunderstanding about the gas exchange process. During gas exchange, the focus is on the enhancement of blood oxygen levels rather than deficiency. The correct action is that blood becomes enriched with oxygen as it passes through the alveoli, not deficient in it.

Regarding the other options, carbon dioxide is not absorbed into the blood; instead, it is removed from the blood into the alveoli to be exhaled. Furthermore, oxygen is not expelled into the air during this exchange; it is absorbed into the bloodstream. Lastly, the blood leaving the lungs is rich in oxygen and low in carbon dioxide, in contrast to any suggestion that it is rich in CO2.