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 the housing problem for young and middle-aged teachers. The principals who are solving the problem of young and middle-aged teachers' housing are not the principals who manage well. 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 the welfare of teachers.', 'The proportion of young and middle-aged teachers has generally increased significantly in recent years.', "All principals who first focus on solving the problem of young and middle-aged teachers' housing are principals who manage well."]