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': 'Microfflaria endemicity index is - \nSelect and explain. \nA. % of persons showing MF in blood and diseased individual, B. % of persons showing MF in blood only, C. Number of MF in the blood, D. Average no. persons with positive slides', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]