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
The maximum ozone concentration in the polluted atmosphere is dependent on the concentration and ratio of nitrogen oxides and 
Select and explain. 
A. Carbon monoxide, B. Lead, C. volatile organic compounds, D. Sulphur dioxide
C: volatile organic compounds
Answer: C: volatile organic compounds 
Explanation: Ozone is formed by the photochemical reaction of sunlight with pollutants such as nitrogen oxides from vehicles, industrial emissions and volatile organic compounds. The highest level of ozone pollution occurs during periods of sunny weather. Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 794