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': 'Contrast material used in the diagnosis of esophageal atresia is: \nSelect and explain. \nA. Barium swallow, B. Gastrograffin, C. Conray, D. Dianosil', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Dianosil', 'role': 'assistant'}]