Of patients over 65 years old who survived [url=]coronary [/url][C1] [url=]bypass surgery[/url][C2] —a procedure widely prescribed for people with heart disease—only 75 percent benefited from the surgery.
Thus it appears that for one in four such patients, the doctors who advised them to undergo this surgery, with its attendant risks and expense, were more interested in an opportunity to practice their skills and in their fee than in helping the patient.
Which of the following, if true, most seriously undermines the argument?
A [url=]Many of the patients who receive coronary bypass surgery are less than 55 years old.
[/url]B Possible benefits of coronary bypass surgery include both relief from troubling symptoms and prolongation of life.
C Most of the patients in the survey decided to undergo coronary bypass surgery because they were advised that the surgery would reduce their risk of future heart attacks.
D [C3] [url=]The patients over 65 years old who did not benefit from the coronary bypass surgery were as fully informed as those who did benefit from the surgery as to the risks of the surgery prior to undergoing it.[/url][C4]
E [url=]The patients who underwent coronary bypass surgery but who did not benefit from it were medically indistinguishable, prior to their surgery, from the patients who did benefit[/url] E正确。
因为如果医生在手术前不知道手上的病人会不会benefit from the surgery,那么他们就无从决定自己为病人动手术的动机。
不过我的问题是：为什么不选A呢？ 原文是说65岁以上的人有四分之一的概率无法从手术受益，从而推出有四分之一的概率医生是在为自己“练手”而让病人开刀。
如果做手术的大部分都是55岁以下的人，那是不是根本就推不出这个四分之一，从而削弱结论呢？
请各位指教指教。。 | 
