This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
[{'content': "Best investigation for Zenker's diverticulum is: \nSelect and explain. \nA. Barium swallow, B. Endoscopy, C. CECT, D. EUS", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. (a) Barium swallowRef: Sabiston 20th Edition, Page 1020-1022* IOC for Zenker's - Barium swallow* IOC for Achalasia - Manometry* IOC for Barret's - Endoscopic biopsy", 'role': 'assistant'}]