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: Social & Preventive Medicine
[{'content': 'Birth length of the baby doubles at \nSelect and explain. \nA. 6 months of age, B. 1 year of age, C. 2 years of age, D. 4 years of age', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]