Naughty students

When you started working as a teacher, you had hopes of spreading the light of knowledge, but for a year your students did nothing but laugh at you and neglect the subject. Now it's time for revenge - they failed the exam and are waiting for a retake, standing outside your office. You announced that only one of them will be able to retake it. P.S. All girls have reached adulthood. You can ask them yourself.