**Core Concept**
The question is testing the pharmacological management of Alzheimer's disease, a neurodegenerative disorder characterized by progressive cognitive decline. The treatment involves cholinesterase inhibitors and N-methyl-D-aspartate (NMDA) receptor antagonists.

**Why the Correct Answer is Right**
Donepezil, a cholinesterase inhibitor, works by increasing the concentration of acetylcholine in the brain by preventing its breakdown. This helps to improve cognitive function in patients with Alzheimer's disease. Donepezil selectively inhibits acetylcholinesterase, the enzyme responsible for breaking down acetylcholine, thereby increasing the availability of acetylcholine for neurotransmission.

**Why Each Wrong Option is Incorrect**
**Option A:** Tacrolimus is an immunosuppressive agent used to prevent rejection in organ transplantation and treat autoimmune diseases, not Alzheimer's disease.
**Option B:** Ropinirole is a dopamine agonist used to treat Parkinson's disease and restless legs syndrome, not Alzheimer's disease.
**Option C:** Lisinopril is an angiotensin-converting enzyme (ACE) inhibitor used to treat hypertension and heart failure, not Alzheimer's disease.

**Clinical Pearl / High-Yield Fact**
Cholinesterase inhibitors like donepezil are most effective in the early stages of Alzheimer's disease and can improve cognitive function, but do not slow disease progression.

**Correct Answer:** C. Donepezil.