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': 'Amyl nitrate inhalation test is used to detect- \nSelect and explain. \nA. Carcinoma esophagus, B. Achalasia cardia, C. Oesophageal diverticulum, D. Transeoesophageal fistula', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]