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 concavity at the root of the nose is used as a third point of reference with \nSelect and explain. \nA. Whipmix average axis facebow, B. Hanau, C. Dentatus, D. Kayo', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]