The hearts of patients who are given vitamin E before undergoing heart surgery are less susceptible to certain postoperative complications than are the hearts of patients who are not given vitamin E before heart surgery. From six hours after surgery onward, however, the survivors from both groups show the same level of heart function, on average, and also recover equally well. Despite this lack of long-term effect, doctors often recommend vitamin E for patients about to undergo heart surgery. Which one of the following, if true, most helps to explain the doctors' recommendation? ['Many patients who are told that they are being given vitamin E actually receive a medically inert substance.', 'Postoperative complications occur six or more hours after surgery for some patients who have not been given vitamin E.', 'Postoperative complications pose the greatest threat to patients during the first six hours after heart surgery.', 'Certain categories of patients are inherently less likely to develop postoperative complications than other patients are.']