This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Concept of health and disease, Subject name: Social & Preventive Medicine
[{'content': 'Sullivan index is an index for \nSelect and explain. \nA. Life free of disability, B. Life Expectancy, C. Earning capacity, D. Population index', 'role': 'user'}, {'content': "Answer: A \nExplanation: Sullivan's index also known as Disability Free Life Expectancy (DFLE) is a method to compute life expectancy free of disability. It is calculated by formula:Life expectancy minus duration of disability Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 26", 'role': 'assistant'}]