This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and Health, Subject name: Social & Preventive Medicine
In Indoor air pollution, carbon monoxide is produced by 
Select and explain. 
A. Combustion equipment, B. Stove, C. Gas heaters, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: (All of the above) (593 - Park 19th) (642-Park 20th)Sources of Indoor air pollutantsPollutantSources* Respirable particle* Carbon monoxide* Nitrogen - dioxide* Sulphur dioxide* Formaldehyde* Ozone* Radon and daughters* Asbestos* Mineral fibresTobacco smoke, stove, Aerosol spraysCombustion equipment, stove, Gas heatersGas cookers, cigarettesCoal combustionParticle board, carpet adhesives insulationElectric arcing, UV light sourcesBuilding materialInsulation, fire proofingAppliances