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. Ewings sarcoma, B. SLL, C. Dermatofibroma protuberans, D. Malignant Histiocytic fibroma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Refer Harrison 17th/613', 'role': 'assistant'}]