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 zone of dentin most recently formed and uncalcified is known as: \nSelect and explain. \nA. Mantle dentin, B. Circumpulpal dentin, C. Predentin, D. Secondary dentin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]