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: Medicine
[{'content': 'A patient of multiple myeloma presents with bony lesions. What is the best marker for prognosis of the disease: \nSelect and explain. \nA. Bone marrow plasma cell, B. Serum calcium level, C. Beta 2 microglobulin, D. Beta 1 microglobulin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Answer is C (b2 microglobulin): Serum b2 microglobulin is the single most powerful predictor of survival and can substitute for staging-H-16th', 'role': 'assistant'}]