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
TATA memorial hospital conducted a cohort study on 7000 subjects who were smokers over a ten-year period& found 70 subjects developed lung cancer. Concurrent evaluation of general population in the catchment area of hospital, out of 7000 non-smoker subjects only 7 developed lung cancer. The RR for developing lung cancer is 
Select and explain. 
A. 1, B. 10, C. 100, D. 0.1
B: 10
Answer: B: 10 
Explanation: TATA memorial hospital conducted a cohort study on 7000 subjects who were smokers over a tenyear period & found 70 subjects developed lung cancer,
Thus, Iexp = × 1000 = 10 per thousand
Also, concurrent evaluation of general population in the catchment area of hospital, out of 7000 non-smoker subjects only 7 developed lung cancer,
Thus, Inon-exp = × 1000 = 1 per 1000
Therefore, RR = 10 per 1000/ 1 per 1000
= 10