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': 'Which of the following stage of tooth formation is characterized by the commencement of mineralization and root formation: \nSelect and explain. \nA. Bud stage., B. Cap stage., C. Bell stage., D. Advanced bell stage.', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Mineralization and root formation is the characteristic feature of Advanced bell stage.', 'role': 'assistant'}]