Which gas is a byproduct of respiration?

The correct answer is carbon dioxide because it is a natural byproduct of the process of cellular respiration, which occurs in living organisms. During respiration, cells convert glucose and oxygen into energy, with carbon dioxide and water being released as waste products. This reaction is vital for producing the energy needed for various cellular activities.

In contrast, oxygen is consumed during respiration, as it is necessary for the process to take place. Nitrogen is a major component of the atmosphere but is not involved in the respiratory process of living organisms in producing energy. Hydrogen does not play a direct role in respiration either and is not produced as a waste product in this context. Therefore, carbon dioxide is definitively recognized as the gas that results from the metabolic process of respiration.