There are 8 people in the dorm room of a university, three are Cantonese, one is Beijinger, two are northerners, one is a guarantee student, and three are poor students. Assuming that the above introduction involves all the students in the dormitory, Which of the following judgments and questions about the students in the dormitory are contradictory:. ['Students sent from the North.', 'Beijingers are neither a guarantee nor a poor student.', 'Two poor students are Cantonese.', 'None of the students from Heilongjiang.']