This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'The indication for the use of Kloehn type cervical head gear is in: \nSelect and explain. \nA. Maxillary retrusion, B. Maxillary protrusion, C. Mandibular prognathism, D. Mandibular retrognathism', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]