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': 'Most commonly associated ion with remineralisation of enamel \nSelect and explain. \nA. Ca+2, B. F–, C. Po4–2, D. K+', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]