This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disease Causation, Measurements, Milestones, Subject name: Social & Preventive Medicine
[{'content': 'In a population of 5000, number of new cases of TB is 500; old cases in the same population are 150. What is the prevalence of TB? \nSelect and explain. \nA. 9%, B. 12%, C. 13%, D. 18%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Prevalence = total number of cases / total population x 100 = (650/5000) x100 =13%', 'role': 'assistant'}]