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': 'Maxillary protraction head gear is used for \nSelect and explain. \nA. Max. skeletal protrusion, B. Mandibular skeletal retrusion, C. Bimaxillary protrusion, D. Skeletal open bite', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]