Some physics teachers at Zhiyuan High School have obtained a master's degree. The physics teachers who have gone to the master's degree have more than three years of teaching experience. Some female teachers also have more than three years of teaching experience. All female teachers are married. Based on the above text, which of the following must be correct ?:. [' physics teachers have more than three years of teaching experience.', 'There may be male teachers who are not yet married.', " physics teachers who have obtained a master's degree are married.", "Physics teachers who may have master's degrees are female teachers."]