What is the function of the respiratory system?

• A. Filter toxins from blood
• B. Regulate body temperature
• C. Produce digestive enzymes
• D. Supply the body with oxygen and dispose of carbon dioxide

Answer: (D)

Gas exchange is the main job of the respiratory system: it brings in the oxygen we need for energy and removes the carbon dioxide that cells produce as waste. Air is drawn into the lungs, reaches tiny sacs called alveoli where oxygen diffuses into the blood and binds to hemoglobin for delivery to tissues. At the same time, carbon dioxide diffuses from the blood into the alveoli to be exhaled. This exchange supports cellular respiration and helps maintain the body's pH. During exercise, increased breathing helps supply more oxygen and remove CO2 more quickly, supporting performance and recovery. Other options describe functions of different body systems: filtering toxins is mainly done by the liver and kidneys, regulating body temperature involves the skin and circulatory system, and producing digestive enzymes comes from the digestive tract.