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: Surgery
[{'content': 'Antenatal double bubble appearance on ultrasound is due to - \nSelect and explain. \nA. Diaphragmatic hernia, B. Duodenal atresia, C. Gastric volvulus, D. Intussusception', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]