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: Surgery
[{'content': "The neonatal kidney achieves concentrating ability equivalent to adult's kidney by - \nSelect and explain. \nA. One year of age, B. Eighteen months of age, C. Three to six months of age, D. Just before puberty", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]