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': "Double bubble sign is a radiological feature of: \nSelect and explain. \nA. Pyloric stenosis, B. Duodenal atresia, C. Hirschsprung's disease, D. Necrotising enterocolitis", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Duodenal atresia', 'role': 'assistant'}]