This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Concept of health and disease, Subject name: Social & Preventive Medicine
The impoance of defining "population at risk" in an epidemic is 
Select and explain. 
A. Conduct survey, B. Search for deaths, C. Calculate attack rates, D. Prepare case sheet
C: Calculate attack rates
Answer: C: Calculate attack rates 
Explanation: The population census will help in computing the much-needed attack rates in various groups and subgroups of the population.Without an appropriate denominator of &;&;population at risk,&; attack rates cannot be calculated.Ref: Park 23rd edition pg: 130