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 for Zenker's diverticulum is: \nSelect and explain. \nA. CECT, B. Endoscopy, C. Esophageal manometry, D. Barium Swallow", 'role': 'user'}, {'content': 'Answer: D \nExplanation: "Once suspected, the diagnosis is established by a barium swallow. Endoscopy is usually difficult in the presence of a cricopharyngeal diverticulum; and potentially dangerous, owing to obstruction of the true esophageal lumen by the diverticulum and the attendant risk of diverticular perforation."- Schwartz', 'role': 'assistant'}]