This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'The normal intrapleural pressure at the start/beginning of inspiration is ………………………………. cm of H20 \nSelect and explain. \nA. –7.5, B. –5.0, C. –2.0, D. –0.5', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The intrapleural pressure becomes more negative at the end of inspiration and less negative at expiration. \nIt ranges between -3 and -6 mmHg. At the beginning of inspiration, the pressure is -3.8mmHg (-5 cm of water), and at the end of inspiration (beginning of expiration), it is -6mmHg ( -8 cm of water).\xa0\nThe elasticity of lung and rib cage causes it to recoil and thus creating the negative pressure.\xa0\nThe lymphatic drainage of the pleural fluid also creates a negative pressure.', 'role': 'assistant'}]