This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 1, Subject name: Physiology
Residual volume is:- 
Select and explain. 
A. Equal to the dead space volume, B. Amount of air in the lungs after maximal forceful inspiration, C. Amount of air remaining in the lungs at the end of normal expiration, D. Total lung capacity minus vital capacity
D: Total lung capacity minus vital capacity
Answer: D: Total lung capacity minus vital capacity 
Explanation: RV = Total lung capacity minus vital capacity. RV is volume remained in lungs after forceful expiration.