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
Pressure - volume curves in the lung is given here. The pressure-volume curves of the total respiratory system (PTR), lungs (PL), and chest wall (Pw) are plotted together with standard lung volumes. Point A indicate which of the following? 
Select and explain. 
A. Closing volume of lung, B. Resting lung volume, C. Residual volume of lung, D. Expiratory reserve volume
B: Resting lung volume
Answer: B: Resting lung volume 
Explanation: Ans. B. Resting lung volumeThe pressure is zero at a lung volume that corresponds to the volume of gas in the lungs at FRC is also known as Resting Respiratory volume/capacity because the opposing forces like the elastic recoil of the lungs and the chest wall are equal and they balance each other at FRC.