This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Musculoskeletal system, Subject name: Anatomy
[{'content': "CD-99 is for \nSelect and explain. \nA. A. Ewing's sarcoma, B. B. Sll, C. C. Dermatofibroma protrubens, D. D. Malignant histocytic fibroma", 'role': 'user'}, {'content': "Answer: A \nExplanation: CD 99 is a marker associated with the diagnosis of Ewing's sarcoma Granulosa cell tumor is also often found to be associated to CD 99", 'role': 'assistant'}]