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: Medicine
[{'content': 'In an emphysematous patient with humus leison which is the best investigation to measure lung volumes ? \nSelect and explain. \nA. Body plethysmography, B. Helium dilution, C. Trans diaphragmatic pressure, D. DLCO', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]