This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdominal Radiography, Subject name: Radiology
[{'content': 'Bird beak appearance on barium swallow study in seen in - \nSelect and explain. \nA. Achlasia cardia, B. Carcinoma esophagus, C. Hiatus hernia, D. Diffuse esophageal spasm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., Achlasia cardia o \'\'Bird beak appearance on barium study is seen in achlasia cardia.Important esophageal signsSignConditionRat tail appearance of esophagus MaharashtraEsophageal carcinomaMegaesophagus (sigmoid esophagus)"Bird beak" appearanceHurst phenomenonAchalasia cardiaYo-Yo motion of barium "Corkscrew" appearance(esophageal curling)Rosary-bead/sheikh kebab configurationChain of bead appearanceDiffuse esophageal spasm', 'role': 'assistant'}]