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: Radiology
[{'content': 'Rat – tail appearance on barium swallow examination is seen in – \nSelect and explain. \nA. Achalasia cardia, B. Carcinoma esophagus, C. Hiatus hernia, D. Diffuse esophageal spasm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: "Rat-tail" appearance on barium study is seen in carcinoma esophagus.', 'role': 'assistant'}]