This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
Progressive multifocal leukoencephaloPathy is caused- 
Select and explain. 
A. Epstein-barr virus, B. Varicella-zoster virus, C. Cytomegalo Virus, D. JC Papovavirus
D: JC Papovavirus
Answer: D: JC Papovavirus 
Explanation: Harrison's principles of internal medicine. *In PML oligodendrocytes have enlarged densely staining nuclei that contain viral inclusions formed by crystallinearrays of JC virus paicles.