**Core Concept**
Neurofibrillary tangles (NFTs) are abnormal protein aggregates found in neurons, composed of hyperphosphorylated tau protein. This accumulation is a hallmark of neurodegenerative diseases, particularly Alzheimer's disease. The formation of NFTs disrupts normal neuronal function, leading to cognitive decline and neuronal death.

**Why the Correct Answer is Right**
The correct formation of neurofibrillary tangles involves the hyperphosphorylation of tau protein, which is normally involved in microtubule assembly and stability. In Alzheimer's disease, the enzyme glycogen synthase kinase-3β (GSK-3β) plays a key role in tau hyperphosphorylation. As a result, tau protein becomes abnormally phosphorylated, leading to its aggregation into insoluble fibrils that form neurofibrillary tangles. This process is a critical component of Alzheimer's disease pathology.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because neurofibrillary tangles are not typically associated with Huntington's disease, which is characterized by the expansion of CAG repeats in the Huntingtin gene.
**Option B:** This option is incorrect because Lewy bodies are composed of α-synuclein protein and are a hallmark of Parkinson's disease and dementia with Lewy bodies.
**Option C:** This option is incorrect because Pick bodies are composed of tau protein but are a specific type of tau inclusion body seen in frontotemporal dementia with parkinsonism-17 (FTDP-17).

**Clinical Pearl / High-Yield Fact**
Remember that neurofibrillary tangles are a key histopathological feature of Alzheimer's disease, which is the most common cause of dementia worldwide.

**Correct Answer: D. Alzheimer's disease. Alzheimer's disease.**