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': "Investigation of choice in Hirschsprung's disease is \nSelect and explain. \nA. Barium swallow, B. CECT, C. Barium enema, D. Rectal biopsy", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Rectal biopsy is defn diagnosis. Affected part has no ganglions.', 'role': 'assistant'}]