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': "Registration point: \nSelect and explain. \nA. Point 'A', B. A point half way on the perpendicular from sella to Boltons plane, C. Nasion, D. Point 'B'", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]