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 apical foramen of a fully developed permanent tooth is usually tined by \nSelect and explain. \nA. Dentin, B. Cementum, C. Epithelial rest cells, D. The Epithelial diaphragm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]