An older adult experiencing a progressively worsening memory and cognition for past two years may be experiencing which one of the following diseases?

A. Delirium is an acute, often sudden onset of confusion and altered mental status, usually caused by an underlying medical condition or medication. It tends to fluctuate and is typically reversible — not consistent with the progressive and long-term decline described. B. Amnesia refers specifically to memory loss, which can be caused by trauma, disease, or psychological factors, but it does not encompass the broader cognitive decline (such as impaired judgment, language, and executive function) seen in dementia. C. Dementia is characterized by a gradual and progressive decline in memory, thinking, and reasoning skills over time. The two-year progression described in the question is typical of dementia, especially in older adults. D. Parkinson’s disease is a neurodegenerative disorder primarily affecting movement.While it can be associated with dementia in later stages, the primary symptoms early on are related to motor function (e.g., tremors, rigidity), not memory and cognition.