Of patients over 65 years old who survived coronary bypass surgery-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?

【选项】Many of the patients who receive coronary bypass surgery are less than 55 years old.