Question

The gas that diffuses from blood to lungs is ...........

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

Answer 1

The correct option is B Carbon dioxide

• The gas exchange takes place in the millions of alveoli in the lungs and the capillaries that envelop them.
• The Inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide moves from the blood in the capillaries to the air in the alveoli, as the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli.
• Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli. Hence, the gas that diffuses from blood to lungs is carbon dioxide.

So, the correct answer is 'carbon dioxide'.