Which gas is primarily expelled from the body during exhalation?

• A. Oxygen
• B. Nitrogen
• C. Carbon dioxide
• D. Hydrogen

Answer: (C)

During exhalation, the primary gas expelled from the body is carbon dioxide. This occurs as a result of the metabolic processes that take place in the cells of the body. When cells use oxygen to produce energy, they generate carbon dioxide as a waste product.

The respiratory system plays a crucial role in regulating the levels of carbon dioxide in the blood. When carbon dioxide levels rise, it triggers the urge to breathe, facilitating the removal of this gas through exhalation. The process is essential for maintaining the acid-base balance in the body, as an excess of carbon dioxide can lead to respiratory acidosis.

In contrast, while oxygen is inhaled and utilized by the body, it is not the major gas expelled during exhalation. Nitrogen is typically inert and constitutes a large part of the air we breathe, but it is not actively exchanged in the respiratory process. Hydrogen is not a significant component of exhaled air under normal circumstances. Thus, carbon dioxide is clearly the primary gas removed from the body during exhalation, confirming it as the correct answer.