allerySurfactant in the alveoli
Aabsorbs CO₂ from blood directly
Btransports O₂ into capillaries
Cfilters dust particles from inhaled air
Dlowers surface tension so alveoli don't collapse
Answer & Solution
Correct answer: D. lowers surface tension so alveoli don't collapse
Surfactant is a lipid-protein mixture (mainly dipalmitoyl phosphatidylcholine) secreted by type II alveolar cells.
It lowers surface tension in the thin layer of water lining alveoli, preventing collapse during expiration.
Premature babies often lack it (respiratory distress syndrome).
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