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
The cell mass in multiple myeloma is formed by- 
Select and explain. 
A. Circulating B cells settle in BM, B. Preformed B cells are seen in the marrow, C. Circulating B cells settle in BM, D. B-cells turn malignant and secrete light chains
D: B-cells turn malignant and secrete light chains
Answer: D: B-cells turn malignant and secrete light chains 
Explanation: None