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': 'X-rays findings of "Fibrous Dysplasia" is: \nSelect and explain. \nA. Ground glass density, B. Calcifications, C. Coical thickening, D. Bony expansion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ground glass density', 'role': 'assistant'}]