An 80-year-old person has started forgetting the names of familiar persons and places. There has been confabulation. He tends to forget whether he has had his meals. Clinical and neurological examination reveals no abnormality.CT scan of the brain showed symmetrical enlargement of lateral ventricles and wider sulci. The most likely diagnosis is-
Confusional state
Alzheimer's disease
Alcholol dementia
Chronic cerebrovascular insufficiency