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
Regarding Progressive multifocal leucoence- phalopathy, all are true, except -a) Caused by JC virusb) Diffuse cortical matter involvementc) Disease of white matterd) Disease of grey matter 
Select and explain. 
A. a, B. bc, C. ad, D. ac
D: ac
Answer: D: ac 
Explanation: None