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': "According to Stone and Church's classification, John, age\n4, can be classified developmentally as: \nSelect and explain. \nA. Toddler, B. Preschooler, C. Middle years child, D. Adolescent", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]