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': 'Non visualization of gastric fundic bubble with air-fluid level in retrocardiac region suggests:September 20003 \nSelect and explain. \nA. Carcinoma esophagus, B. Esophageal web, C. Achalasia cardia, D. Congenital hyperophic pyloric stenosis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C i.e. Achalasia cardia', 'role': 'assistant'}]