Question

practice ii
lo 4.2. what is the primary gas exchange by the respiratory system?
carbon dioxide and water vapor
carbon monoxide and hydrogen
hydrogen and nitrogen
oxygen and carbon dioxide
nitrogen and carbon dioxide

Explanation:

The respiratory system's main function is gas exchange. Inhaled air has oxygen ($O_2$), which is taken into the blood. Exhaled air has carbon dioxide ($CO_2$), which is removed from the body. Other gas pairs like carbon monoxide - hydrogen, hydrogen - nitrogen, etc., are not the primary gases involved in normal respiratory gas exchange.

Answer:

Oxygen and Carbon Dioxide