Tissue biopsies taken on patients who have undergone throat surgery show that those who snored frequently were significantly more likely to have serious abnormalities in their throat muscles than those who snored rarely or not at all. This shows that snoring can damage the throat of the snorer. Which one of the following, if true, most strengthens the argument? ['People who have undergone throat surgery are no more likely to snore than people who have not undergone throat surgery.', 'The abnormalities in the throat muscles discovered in the study do not cause snoring.', "The patients' throat surgery was not undertaken to treat abnormalities in their throat muscles.", "The study relied on the subjects' self-reporting to determine whether or not they snored frequently."]