The lungs remain inflated because .a. intrapleural pressure is exactly equal to atmospheric pressure b. intrapleural pressure is exactly equal to intrapulmonary pressure c. intrapleural pressure is less than intrapulmonary pressure d. intrapulmonary pressure is less than intrapleural pressure

Option C,  Intrapleural pressure is less than intrapulmonary pressure

Explanation:

During inspiration, the air enters the lungs due to lower pressure in the intrapulmonary or intra-alveolar  than the atmospheric pressure. During quite respiration, the intrapulmonary pressure reduces to a pressure that is 3 mm Hg lower than that of atmospheric pressure. During quiet expiration, the intrapulmonary pressure rises up to a pressure that is 3 mm Hg higher than that of atmospheric pressure. This leads to lack of air in the intrapleural space thereby producing intrapleural pressure which is lesser than that of intrapulmonary pressure.  

This difference in pressure (i.e higher pressure with in the lungs than the atmosphere)  causes lungs to remain attached to the chest wall and hence looks inflated.  

Hence, option C is correct

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