In a study of heart patients awaiting treatment for reduced blood flow to the heart, those still waiting to find out whether they would need surgery were less likely to experience pain from the condition than were those who knew what type of treatment they would receive. Assuming that this uncertainty is more stressful than knowing what one' s future holds, then it is reasonable to conclude that__. Which one of the following most logically completes the argument? ['stress sometimes reduces the amount of pain a heart patient experiences', 'heart patients suffering from reduced blood flow to the heart who are experiencing pain from the condition are more likely to require surgery than are such patients who are not experiencing pain', "the severity of a heart patient's condition is usually worsened by withholding information from the patient about the treatment that that patient will receive", 'stress is probably an effect rather than a cause of reduced blood flow to the heart']