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': 'Disease rate is \nSelect and explain. \nA. Risk of susceptibility, B. Prevalence rate, C. Time period in a calendar year, D. Disease occurrence in a specified time period', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Attack rate (case rate or diesease rate):it is an incidence rateusually expressed in percentused only when population is exposed to risk for a limited period of time such as during an epidemicattack rate = (no. of new cases of a specified disease during a specified time interval / total population at risk during the same interval) x 100ref: Park&;s 23rd edition pg 61', 'role': 'assistant'}]