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': 'Bird beak appearance on barium swallow study is seen in - \nSelect and explain. \nA. Achlasia cardia, B. Carcinoma esophagus, C. Hiatus hernia, D. Diffuse esophageal spasm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: ’’Bird beak appearance on barium study is seen in achalasia cardia.\n\n\xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0Important esophageal signs', 'role': 'assistant'}]