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
Irreversible dementia is caused due to: 
Select and explain. 
A. Subarachnoid hemorrhage, B. Wilson's disease, C. Normal pressure hydrocephalus (NPH), D. Vascular dementia
D: Vascular dementia
Answer: D: Vascular dementia 
Explanation: Vascular dementia is a cause of progressive dementia due to impaired blood supply to the brain.