All principals who really care about teacher welfare are proven to be well-managed principals; while those who really care about teacher welfare first focus on solving middle-aged and young teachers' housing. Therefore, those who don't focus first on solving the problem The principals of the young and middle-aged teachers' housing are not the principals who manage the law properly. In order for the above argument to be true, which of the following must be true? ['The housing problem of young and middle-aged teachers is the most prominent problem in the welfare of teachers.', 'All principals who manage well are principals who care about teacher welfare.', 'The proportion of young and middle-aged teachers has generally increased significantly in recent years.', "All principals who first focus on addressing young and middle-aged teachers' housing are principals who manage well."]