This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
In a village of 1 lakh populations, among 20,000 exposed to smoking, 200 developed cancer, and among 40,000 people enexposed, 40 developed cancer. The relative risk of smoking in the development of cancer is - 
Select and explain. 
A. 20, B. 10, C. 5, D. 15
B: 10
Answer: B: 10 
Explanation: Relative risk = incidence in exposed/incidence of disease in non exposed Relative risk = 1 no association between disease and risk factor >1;there is positive association between disease and risk factor Incidence in exposed =200/20000= Incidence in nonexposed =40/40000 Relative risk = .01/.001 =10 Ref: Parks textbook of preventive and social medicine, 23rd Edition, Pg no: 78