Physician: Hatha yoga is a powerful tool for helping people quit smoking. In a clinical trial, those who practiced hatha yoga for 75 minutes once a week and received individual counseling reduced their smoking and cravings for tobacco as much as did those who went to traditional self-help groups once a week and had individual counseling. Which one of the following is an assumption on which the physician's argument relies? ['People who practice hatha yoga for 75 minutes once a week are not damaging themselves physically.', 'Most smokers are able to practice hatha yoga more than once a week.', 'The individual counseling received by the smokers in the clinical trial who practiced hatha yoga did not help them quit smoking.', 'Traditional self-help groups are powerful tools for helping people quit smoking.']