This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Physiology
A man connected to a body plethysmograph for estimation of FRC inspires against a closed glottis. Which of the following statements is true - 
Select and explain. 
A. The pressure in both the lung and the box increase, B. The pressure in both the lung and the box decrease, C. The pressure in the lung decrease, but that in the box increase, D. The pressure in the lung increase, but that in the box decrease
C: The pressure in the lung decrease, but that in the box increase
Answer: C: The pressure in the lung decrease, but that in the box increase 
Explanation: Ans. (c) The pressure in the lung decrease, but that in the box increase(Ref: Ganong, 25th ed/p.630)Body plethysmography is based on the principle of Boyle's Law which states that volume of a gas is inversely proportional to the pressure of that gas at constant temperatureReciprocal changes in Pressure and volume (Boyle's law) during plethysmography During inspirationDuring expirationIn subject's LungVolume increasesPressure decreasesVolume decreasesPressure increasesIn boxVolume decreasesPressure increasesVolume increasesPressure decreases