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': 'Sign suggestive of carcinoma lung on chest X-ray is: \nSelect and explain. \nA. Rib erosion, B. Central destruction within lesion, C. Flattening of diaphragm, D. Calcification', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Rib erosion', 'role': 'assistant'}]