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: Anatomy
[{'content': "Urachus fistula is - \nSelect and explain. \nA. Patent allantois, B. Ectopic hernia, C. Patent vitello-intestinal tract, D. Meckel's diverticulum", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]