This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Pathology
[{'content': 'CD marker of histiocytosis is- \nSelect and explain. \nA. CD IA, B. CD 1B, C. CD1C, D. CD1D', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Tumour cells in histiocytosis typically express HLA -DR,S-100,and CD1a. Reference : Robbins and Cotran Pathologic basis of disease.South Asia Edition volume 1.page no. 622', 'role': 'assistant'}]