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: Skin
[{'content': 'Rx of refractory histiocytosis? \nSelect and explain. \nA. Cladarabine, B. High dose MTX, C. High dose cytosine arabinoside, D. Fludarabine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A. i.e. Cladarabine', 'role': 'assistant'}]