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
A patient of multiple myeloma presents with bony lesions. What is the best marker for prognosis of the disease: 
Select and explain. 
A. Bone marrow plasma cell, B. Serum calcium level, C. Beta 2 microglobulin, D. Beta 1 microglobulin
C: Beta 2 microglobulin
Answer: C: Beta 2 microglobulin 
Explanation: Answer is C (b2 microglobulin): Serum b2 microglobulin is the single most powerful predictor of survival and can substitute for staging-H-16th