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': 'Patent vitello-intestinal duct should preferably be operated at - \nSelect and explain. \nA. Birth, B. 6 months of age, C. 12 months of age, D. 3 years of age', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]