This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Non communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'Contraceptive efficacy expressed as \nSelect and explain. \nA. 100 women months, B. 1000 women years, C. 100 women years, D. 10 women years', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Contraceptive efficacy is assessed by measuring the number of unplanned pregnancies that occur during a specified period of exposure and use of contraceptive methods.Contraceptive efficacy is measured using Pearl index and life table analysis. Pearl index is number of failure per 100 woman-years of exposure (HWY) HWY=total accidental pregnancies/total months of exposure.*1200 Life table analysis measure failure rate per month of exposure. Park&;s textbook of preventive and social medicine.K Park. Edition 23.Pg no: 510', 'role': 'assistant'}]