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': 'All are true regarding case fatality rate except - \nSelect and explain. \nA. Represents killing power of disease, B. Closely related to virulence, C. Very useful for chronic disease, D. May vary in different epidemic for same disease', 'role': 'user'}, {'content': 'Answer: C \nExplanation: ref: Park&;s 23rd edition pg 58 used for acute infectious diseases like food poisoning, cholera, measles.', 'role': 'assistant'}]