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
Sullivan's Index is 
Select and explain. 
A. Disability Free Life expectancy(DFLE), B. Disability Adjusted Life expectancy(DALE), C. Quality Adjusted Life Expectancy(QALE), D. Health Adjusted Life Expectancy(HALE)
A: Disability Free Life expectancy(DFLE)
Answer: A: Disability Free Life expectancy(DFLE) 
Explanation: Sullivan's Index : Life expectancy - Duration of disability.