This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc. (W.B.C), Subject name: Pathology
[{'content': 'Beta-2 -microglobulin is a tumor marker for \nSelect and explain. \nA. Multiple myeloma, B. Lung cancer, C. Colonic neoplasm, D. Choriocarcinoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Multiple myeloma(Ref: Robbins 9th/pg598-602)Serum b2 microglobulin level <3.5mg/L indicates good prognosis, in multiple myeloma.', 'role': 'assistant'}]