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 population, among 2,000 exposed to smoking, 20 developed lung cancer and among 8,000 unexposed people, 8 developed lung cancer. What is attributable risk- 
Select and explain. 
A. 10%, B. 50%, C. 90%, D. 100%
C: 90%
Answer: C: 90% 
Explanation: This is a coho study. Attributable risk = (incidence in exposed -incidence in nonexposed) /incidence in exposed *100 Incidence in exposed=20/2000 Incidence in nonexposed=8/8000 Attributable risk=(0.01-0.001/.01)*100 = 90% 90% of lung cancer among smokers can be attributed to their smoking Ref: Parks textbook of preventive and social medicine, 23rd Edition Pg no: 78