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: Microbiology
Which virus cause nephropathy in transplant recipients? 
Select and explain. 
A. Jc virus, B. Bk virus, C. SV - 40 virus, D. Merkel cell virus
B: Bk virus
Answer: B: Bk virus 
Explanation: Bk virus caue nephropathy in tranplant recipients.