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 track sign is seen in \nSelect and explain. \nA. Duodenal atresia, B. CHPS, C. Gastric ulcer, D. Achalasia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Double/triple track sign\xa0is seen in congenital hypertrophic pyloric stenosis', 'role': 'assistant'}]