This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Air, Light, Sound, Housing, Radiation, Waste Disposal, Subject name: Social & Preventive Medicine
[{'content': 'Which of the following is not a source of Indoor air pollution? \nSelect and explain. \nA. Carbon monoxide, B. Nitrogen dioxide, C. Radon, D. Mercury vapour', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Sources of Indoor air pollution: Indoor air pollutants Sources Respirable paicles Tobacco, smoke, stove, aerosols Carbon monoxide Combustion equipments, stove, gas, heaters Nitrogen dioxide Gas cookers, cigarettes Sulphur dioxide Coal combustion Carbon dioxide Combustion, respiration Formaldehyde Paicle board, carpet adhesives, insulation Organic vapours (benzene, toulidine) Solvents, adhesives, resins, aerosols Ozone Electric aecing, UV light Radon Building materials Asbestos Insulation, fire-proofing Mineral fibers Appliances', 'role': 'assistant'}]