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': 'Which of the following is the best parameter to measure air pollution? \nSelect and explain. \nA. SO2, B. CO2, C. CO, D. N20', 'role': 'user'}, {'content': "Answer: A \nExplanation: The best indicators of air pollution are sulphur dioxide (SO2), smoke and suspended paicles. These are monitored on a daily basis over several sites. The results are then collected by a central agency. Methods for monitoring air pollution: Sulphur dioxide Smoke or Soiling index Grit and dust measurement Coefficient of haze Air pollution index Ref: Park's Textbook of Social and Preventive Medicine, 19th edition, Page 593.", 'role': 'assistant'}]