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': 'In a class III cavity in an incisor tooth the retentive points are placed: \nSelect and explain. \nA. At the expense of facial and Lingual walls and not in dentin, B. Entirely in dentin, C. In axial wall, D. By placing a groove in the lingual surfaces', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]