This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
[{'content': "Retrocardiac lucency with air fluid level is seen in not related-radiology \nSelect and explain. \nA. Hiatus hernia, B. Distal end esophageal obstruction, C. Eventration of diaphragm, D. Zenker's diveiculum", 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]