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': 'There is a real relationship between the incidences of fracture of anterior teeth and the \nSelect and explain. \nA. caries in those teeth, B. hardness of the enamel, C. hardness of dentin, D. protrusion of those teeth', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]