Mayor: To keep our neighborhoods clean, every street in town will be swept at least once a month. If a neighborhood needs more frequent sweepings, due to excessive dirt from major construction for example, that neighborhood will be qualified for interim sweepings. All requests for interim sweepings from qualified neighborhoods will be satisfied immediately. If all of the mayor's statements are true, then which one of the following must also be true? ['A qualified neighborhood that requests an interim sweeping will have its streets swept more than once a month.', 'All qualified neighborhoods will get their streets swept more than once a month.', 'No street will be swept more than once a month unless it is located in a qualified neighborhood.', 'All neighborhoods in which construction is under way are qualified neighborhoods.']