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': "Earliest radiological finding of chron's disease \nSelect and explain. \nA. Coable stone appearance, B. Raspberry appearance, C. Aphthous lesions, D. String sign of kantor", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Earliest change are aphthous lesions or erosions.', 'role': 'assistant'}]