**Core Concept**
Bell's Palsy is an idiopathic peripheral **seventh cranial nerve (facial nerve)** disorder, characterized by sudden onset of **facial muscle weakness** or **paralysis**. The condition results from inflammation and compression of the facial nerve.

**Why the Correct Answer is Right**
The correct answer is related to the **pathophysiology** of Bell's Palsy, which involves **demyelination** and **axonal degeneration** of the facial nerve, leading to **muscle weakness** or **paralysis**. The **inflammation** causes **nerve compression**, affecting the **motor functions** of the face.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it doesn't specify the characteristic features of Bell's Palsy.
**Option B:** Incorrect as it's not directly related to the primary characteristics of the condition.
**Option C:** Incorrect because, although it may be a symptom, it's not the defining characteristic.
**Option D:** Incorrect as it's unrelated to the primary **neurological** features of Bell's Palsy.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **Bell's Palsy** often presents with **sudden onset of unilateral facial weakness**, which can be distinguished from other conditions like **stroke** by the lack of **limb weakness** or **speech disturbances**.

**Correct Answer:** D. Unilateral lower motor neuron weakness of the facial nerve.