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': 'Cementum formation is seen \nSelect and explain. \nA. After dentin formation, B. Before dentin formation, C. Both are formed at same time, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]