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': "A 3 year old female child presented with skin papules. Which of the following is a marker of Langerhan's cell histiocytosis? \nSelect and explain. \nA. CD 1a, B. CD 3, C. CD 68, D. CD 57", 'role': 'user'}, {'content': 'Answer: A \nExplanation: . CD 1a', 'role': 'assistant'}]