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': 'Principal fibres of periodontal ligament are attached to \nSelect and explain. \nA. Alveolar bone proper, B. Bundle bone, C. Lamellar bone, D. Cortical bone', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]