Since 1990 the percentage of bacterial sinus infections in Aqadestan that are resistant to the antibiotic perxicillin has increased substantially. Bacteria can quickly develop resistance to an antibiotic when it is prescribed indiscriminately or when patients fail to take it as prescribed. Since perxicillin has not been indiscriminately prescribed, health officials hypothesize that the increase in perxicillin-resistant sinus infections is largely due to patients' failure to take this medication as prescribed. Which of the following, if true of Aqadestan, provides most support for the health officials' hypothesis? ['Aqadestani health clinics provide antibiotics to their patients at cost.', 'When it first became available, perxicillin was much more effective in treating bacterial sinus infections than any other antibiotic used for such infections at the time.', 'A large number of Aqadestanis never seek medical help when they have a sinus infection.', 'Many patients who take perxicillin experience severe side effects within the first few days of their prescribed regimen.']