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': 'Contraceptive efficacy is measured by \nSelect and explain. \nA. Pearl Index and Life table analysis, B. Pearl Index only, C. Life table analysis and Couple protection rate, D. Pearl Index and Couple protection rate', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Contraceptive Efficacy: Is assessed by measuring the number of unplanned pregnancies that occur during a specified\xa0period of exposure and use of a contraceptive method. Two methods used are:\n\nPearl Index\nLife table analysis\n\nLife Table Analysis (LTA) as measure of contraceptive efficacy:\n– LTA calculates a failure rate per month of use\n– Better measure than PI', 'role': 'assistant'}]