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
For calculation of incidence denominator is taken as? 
Select and explain. 
A. Mid year population, B. Population at risk, C. Total number of cases, D. Total number of deaths
B: Population at risk
Answer: B: Population at risk 
Explanation: Ans. is 'b' i.e., Population at risk o Denominator for calculating incidence is population at risk