If the research was to estimate quality-adjusted life-years lost due to obesity and knee osteoarthritis among Americans aged 50 to 84 years, the best title of the paper would be （）.
A.quality-adjusted life-years lost and obesity and knee osteoarthritis in older Americans
B.effects of obesity and knee osteoarthritis on life quality of older Americans
C.effects of obesity and knee osteoarthritis on morbidity and mortality in older Americans
D./
正确答案：effects of obesity and knee osteoarthritis on morbidity and mortality in older Americans