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 inorganic component of plaque is primary \nSelect and explain. \nA. Calcium and fluoride, B. Calcium and sodium, C. Calcium and phosphorus, D. Sodium and calcium', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]