What essential component do the lungs supply to the blood?

The lungs are responsible for the process of gas exchange in the body, a vital function that involves transferring oxygen into the bloodstream while removing carbon dioxide. During inhalation, oxygen from the air enters the alveoli—tiny air sacs in the lungs—where it then diffuses across the alveolar walls into the capillaries. This oxygen-rich blood is then carried throughout the body to supply tissues and organs.

Oxygen is essential for cellular respiration, the process by which cells produce energy. Without an adequate supply of oxygen, cells would not be able to perform their functions effectively, leading to cellular and, ultimately, systemic dysfunction.

While carbon dioxide is a byproduct of metabolism that is expelled from the body via the lungs, the primary role of the lungs in gas exchange is to increase the oxygenation of blood. Nitrogen is abundant in the atmosphere but does not play a direct role in the body's respiratory function, and hydrogen is not an essential component supplied by the lungs. Thus, the correct answer highlights the fundamental role of the lungs in supplying oxygen to the blood for overall health and metabolic processes.