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
Investigation of choice in hirschsprug's disease is - 
Select and explain. 
A. Rectal manometry, B. Rectal examination, C. Rectal biopsy, D. Ba enema
C: Rectal biopsy
Answer: C: Rectal biopsy 
Explanation: 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.