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': 'Formula of hydroxyapatite crystal is \nSelect and explain. \nA. Ca3 (Po4)2. CaCo3, B. 3Ca(Po4)2. Ca(OH)2, C. CaPo4. Ca(OH)2, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]