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': 'All of the following aEURoeCDaEUR markers used for diagnostic criteria for systemic mastocytosis EXCEPT \nSelect and explain. \nA. CD, B. CD 25, C. CD 117, D. CD 20', 'role': 'user'}, {'content': 'Answer: D \nExplanation: . CD 20', 'role': 'assistant'}]