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
Anatomical dead space measured by - 
Select and explain. 
A. Bohler's method, B. Xenon dilution technique, C. Spirometry, D. Single breath nitrogen test
D: Single breath nitrogen test
Answer: D: Single breath nitrogen test 
Explanation: Ans. D. Single breath nitrogen test(Ref: Ganong 25/e p633, 634, 24/e p633, 634)Anatomical dead space - Calculation:By Bohr's equation - Uses single breath nitrogen inhalation technique.Xenon/Helium dilution technique:Used to measure functional residual capacity of lung.Spirometry:Cannot measure residual or dead space volumes.