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 hirschsprug's disease is - \nSelect and explain. \nA. Rectal manometry, B. Rectal examination, C. Rectal biopsy, D. Ba enema", 'role': 'user'}, {'content': "Answer: C \nExplanation: Definitive diagnosis is made by rectal biopsy. The histopathology of Hirschprung's disease is the absence of ganglion cells in the nerve plexus, presence of hypertrophied nerve bundles and increased acetykholinesterase-positive nerve fibres.", 'role': 'assistant'}]