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: Unknown
[{'content': 'Specific marker for GIST is? \nSelect and explain. \nA. CD 117, B. CD 34, C. CD 23, D. S-100', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., CD 117", 'role': 'assistant'}]