Identifying gas exchange components in alveolus diagram

Steps:

• In alveoli, oxygen (O₂) is present in inhaled air for diffusion into blood.
• Carbon dioxide (CO₂) is carried in blood from body tissues to alveoli for exhalation.
• Red blood cells in capillaries transport O₂ and CO₂ via hemoglobin.
• Labels P, Q, R correspond to O₂ in alveolus, CO₂ in blood, and red blood cell.

Why C is correct:

• C matches the diffusion process where O₂ moves from alveolus (P) to blood, CO₂ from blood (Q) to alveolus, and red blood cells (R) facilitate gas transport per Fick's law of diffusion.

Why the others are wrong:

• A reverses gases, contradicting O₂ intake and CO₂ removal.
• B reverses gases and incorrectly identifies white blood cell, which does not carry gases.
• D reverses gases and specifies white blood cell, irrelevant to oxygen transport.

Final answer: C