Home / Question Bank / Biology / Breathing and Exchange of Gases / Question 3 NEET Biology Class 11 Mechanism of breathing Medium Single correct
During a normal, quiet inspiration in humans, contraction of the diaphragm and the external intercostal muscles brings about a pressure change that draws air into the lungs. Which of the following correctly explains this sequence of events? (A) The diaphragm relaxes and arches upward while the external intercostals contract, decreasing thoracic volume and pressure, which draws air in (B) Both the diaphragm and the intercostal muscles contract to decrease thoracic volume, increasing intra-pulmonary pressure and pushing air out (C) The diaphragm contracts and flattens while the external intercostals lift the ribs and sternum outward, increasing thoracic volume; intra-pulmonary pressure falls below atmospheric pressure, so air flows in (D) Air enters the lungs because the alveoli actively pump air in using ciliary movement, independent of thoracic volume changes Show answer and explanation ← Question 2 All Breathing and Exchange of Gases questions Question 4 → More NEET Biology chapters © 2026 Lumi (Aikolumi Software Pvt Ltd). Original questions written by Lumi. Free to view and practise on this site. Copying, republishing or reproducing these questions, options or solutions, in print or online, is not permitted.
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