Which of the following best describes the lungs?

The lungs are primarily responsible for gas exchange, which is a critical function in the respiratory system. Specifically, they facilitate the process whereby oxygen from the air is transferred into the bloodstream, while carbon dioxide, a waste product of metabolism, is expelled from the blood and exhaled. This exchange occurs in the alveoli, tiny air sacs in the lungs, where oxygen enters the blood, and carbon dioxide exits.

Understanding the lungs' role in gas exchange highlights their vital importance in maintaining proper oxygen levels in the body and removing carbon dioxide, thereby playing an essential part in cellular respiration. This function is key to sustaining life, as all body tissues and organs depend on a consistent supply of oxygen and efficient removal of carbon dioxide for optimal functioning.

The other options describe functions not performed by the lungs: regulating body temperature is primarily managed by the skin and circulatory system; filtering nitrogen waste is a function of the kidneys; and producing blood cells occurs in the bone marrow, not in the lungs.