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': 'After endodontic treatment, the apical foramen is closed due to deposition of: \nSelect and explain. \nA. Bone, B. Cementum., C. GP., D. Sealer.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Cementum is an ideal apical seal after obturation.', 'role': 'assistant'}]