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: Pathology
[{'content': 'CD-99 is marker of : \nSelect and explain. \nA. Ewings sarcoma, B. SLL, C. Dermatofibrosarcoma, D. Malignant fibroma histiocytic tumor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: CD-99 can be used as a tumor\xa0 marker for ewings sarcoma.', 'role': 'assistant'}]