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': 'One of the following is known as Tuberculin Conversion Index \nSelect and explain. \nA. Incidence of disease, B. Prevalence of infection, C. Incidence of infection, D. Prevalence of disease', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]