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
[{'content': 'All are true of attack rate except - \nSelect and explain. \nA. It is type of prevalence rate, B. Expressed as percentage, C. Used when population is exposed to risk for a limited period of time, D. Reflects extent of epidemic', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., It is a type of prevalence rate Attack rate is a type of incidence rate Attack rate It is an incidence rate. It is also known as cumulative incident rate. Usually expressed as a percentage. o Used only when the population is exposed to risk for a limited period of time such as during an epidemic.", 'role': 'assistant'}]