If retail stores experience a decrease in revenues during this holiday season, then either attitudes toward extravagant gift-giving have changed or prices have risen beyond the level most people can afford. If attitudes have changed, then we all have something to celebrate this season. If prices have risen beyond the level most people can afford, then it must be that salaries have not kept pace with rising prices during the past year. Assume the premises above to be true. If salaries have kept pace with rising prices during the past year, which one of the following must be true? ['Attitudes toward extravagant gift-giving have changed.', 'Prices in retail stores have not risen beyond the level that most people can afford during this holiday season.', 'Attitudes toward extravagant gift-giving have not changed, and stores will not experience a decrease in revenues during this holiday season.', 'Either attitudes toward extravagant gift-giving have changed or prices have risen beyond the level that most people can afford during this holiday season.']