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
Which of the following is the best parameter to measure air pollution? 
Select and explain. 
A. SO2, B. CO2, C. CO, D. N20
A: SO2
Answer: A: SO2 
Explanation: 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.