Read the following Assertion and Reason and choose the correct option. Assertion: Diaphragm relaxation causes expiration Reason: The volume of air involved can be measured by using a spirometer

Step-by-step solution

Relaxation of the diaphragm and the inter-costal muscles returns the diaphragm and sternum to their normal positions and reduce the thoracic volume and thereby the pulmonary volume. This leads to an increase in intra-pulmonary pressure to slightly above the atmospheric pressure causing the expulsion of air from the lungs, i.e., expiration.