In the last paragraph the author says, 'On the top floor of the building that housed the lycée dormitory and the sportshall, just next to the infirmary, there was rumoured to be a dentist, and when teachers got angry they would oftenthreaten to send naughty children there.' From this it can be concluded that the teachers threatened to send the students to the dentist when they get angry. Hence, option D is the correct answer.