A college introduced a group of young teachers, some of whom have PhDs in physics. Teachers in physics who have obtained a PhD have more than three years of teaching experience, and some female teachers have more than three years of teaching experience. All-female teachers have married. Based on the above text, the following options must be correct:. ['All physics teachers have more than three years of teaching experience.', 'All Physics teachers who have obtained a PhD are married.', 'Physics teachers who may have obtained a PhD degree are female teachers.', 'There may be male teachers who are not yet married.']