**Core Concept**
Elongated filaments in Pick's disease refer to the abnormal protein aggregates found in the brains of individuals with this neurodegenerative disorder. These filaments are composed of a specific type of protein that is misfolded and accumulates in neurons, leading to neuronal damage and cell death.

**Why the Correct Answer is Right**
The correct answer is tau protein, which is a microtubule-associated protein that is involved in maintaining the structure and stability of microtubules within neurons. In Pick's disease, tau protein becomes hyperphosphorylated and forms abnormal filaments, known as Pick bodies, which are a hallmark of the disease. These filaments disrupt the normal functioning of neurons, leading to the characteristic cognitive and motor symptoms of Pick's disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Pick bodies are not composed of alpha-synuclein, which is a protein associated with other neurodegenerative disorders, such as Parkinson's disease.

**Option B:** This option is incorrect because neurofilaments are composed of three subunits (NF-H, NF-M, and NF-L) and are not typically associated with Pick's disease.

**Option C:** This option is incorrect because ubiquitin is a protein that is involved in the degradation of misfolded proteins, but it is not the primary component of elongated filaments in Pick's disease.

**Clinical Pearl / High-Yield Fact**
Pick's disease is a rare form of frontotemporal dementia, characterized by progressive degeneration of the frontal and temporal lobes of the brain. It is often associated with changes in personality, behavior, and language, and can be distinguished from other forms of dementia by the presence of Pick bodies on histopathological examination.

**Correct Answer:** C.