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': '. A useful index to measure the lethality of an acute infectious diseases is- \nSelect and explain. \nA. Attack rate, B. Incidence rate, C. Case fatality rate, D. None of these', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]