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: Unknown
[{'content': '100 women were surveyed for oral contraceptive pill usage for 24 months, out of which 10 became pregnant. Calculate the pearl index? \nSelect and explain. \nA. 2.5, B. 5, C. 10, D. 20', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ref. Foundations of Community medicine. Page.117\n\xa0\nPearl Index\n\nIt measures the contraceptive efficacy.\nIt is defined as the number of failures per 100 woman\xa0 years of exposure\nThis rate is given by the formula = Total\xa0 accidental \xa0pregnancies * 1200 \n\nNumber of women * Number of month\n\xa0\nPearl Index = 10 ×\xa012 ×\xa0100 / 100 ×\xa024 = 5', 'role': 'assistant'}]