This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
Immunohistochemistry marker of histiocytosis X 
Select and explain. 
A. CD1a, B. CD57, C. CD3, D. CD68
A: CD1a
Answer: A: CD1a 
Explanation: .