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
Multiple myeloma has been seen commonly after exposure to 
Select and explain. 
A. Radioactive isotopes, B. Gold, C. Asbestos, D. Organic dyes
A: Radioactive isotopes
Answer: A: Radioactive isotopes 
Explanation: None