17.   Lists of hospitals have been compiled showing which hospitals have patient death rates exceeding the national average. The data have been adjusted to allow for differences in the ages of patients.

Each of the following, if true, provides a good logical ground for hospitals to object to interpreting rank on these lists as one of the indices of the quality of hospital care EXCEPT:

(A) Rank order might indicate insignificant differences, rather than large differences, in numbers of patient deaths.

(B) Hospitals that keep patients longer are likely to have higher death rates than those that discharge patients earlier but do not record deaths of patients at home after discharge.

(C) Patients who are very old on admission to a hospital are less likely than younger patients to survive the same types of illnesses or surgical procedures.

(D) Some hospitals serve a larger proportion of low-income patients, who tend to be more seriously ill when admitted to a hospital.（C）

(E) For-profit hospitals sometimes do not provide intensive-care units and other expensive services for very sick patients but refer or transfer such patients to other hospitals.

答案是C，我想问一下C的意思是不是只是说明了年轻病人和年老病人的差别，跟医院排名没有关系，属于无关？还有另有说法？

The data have been adjusted to allow for differences in the ages of patients

原题中已经排除了age的影响，所以C不能说明排名有问题。

题目是问以下哪个选项不能用来反对排名的正确性

题目说的是The data have been adjusted to allow for differences in the ages of patients。只是单纯的年纪影响吧，并没有说到年纪大小和生病的关系啊？