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: Social & Preventive Medicine
[{'content': 'Not a constituent of air – \nSelect and explain. \nA. H2, B. N2, C. O2, D. CO2', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Air\xa0\n\nThe immediate environment of man comprises of air on which depends all forms of life.\nThe requirement for air is about 10-20 M3/day.\nThe constituents of air : -\n\n\nMajor → Nitrogen (N2) - 78.1 %, Oxygen (O2) - 20.93%, Carbon dioxide (CO2) - 0.03%\nMinor → Argon, neon, krypton, xenon, helium, water vapour, traces fo ammonia, suspended matter (dust, bacteria, spores, vegetable debris).', 'role': 'assistant'}]