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
The normal intrapleural pressure at the start/beginning of inspiration is ………………………………. cm of H20 
Select and explain. 
A. –7.5, B. –5.0, C. –2.0, D. –0.5
B: –5.0
Answer: B: –5.0 
Explanation: The intrapleural pressure becomes more negative at the end of inspiration and less negative at expiration. 
It 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). 
The elasticity of lung and rib cage causes it to recoil and thus creating the negative pressure. 
The lymphatic drainage of the pleural fluid also creates a negative pressure.