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
[{'content': 'What is the denominator in calculation of incidence - \nSelect and explain. \nA. Number of fresh cases, B. Number of symptomatic cases, C. Total number of cases, D. Population at risk', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Incidence is defined as new cases occurring in a defined population during a specified period of time. Incidence =(number of new cases of specific disease in a given time proof\\population at risk during that period) 100 (refer pgno:60 park 23 rd edition)', 'role': 'assistant'}]