**Core Concept**
Unilateral Recurrent Laryngeal Nerve (RLN) palsy affects the vocal cord on the same side, leading to inspiratory stridor, hoarseness, and dysphonia. The RLN innervates all intrinsic muscles of the larynx except the cricothyroid, which is supplied by the external branch of the superior laryngeal nerve.

**Why the Correct Answer is Right**
Unilateral RLN palsy causes vocal cord paralysis, resulting in a fixed vocal cord position on the affected side. The affected vocal cord is usually in a paramedian or intermediate position, whereas the normal vocal cord is abducted, creating a glottic gap during inspiration. This leads to inspiratory stridor and difficulty breathing in. The cricothyroid muscle, which is spared in RLN palsy, maintains its function, contributing to the characteristic voice change in patients.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as unilateral RLN palsy typically presents with inspiratory stridor and a fixed vocal cord position, not complete airway obstruction.
**Option B:** Incorrect, as the cricothyroid muscle is usually spared in RLN palsy, maintaining its function and contributing to voice changes.
**Option C:** Incorrect, as bilateral RLN palsy would result in complete airway obstruction, whereas unilateral palsy presents with inspiratory stridor.
**Option D:** Incorrect, as the cricothyroid muscle is involved in voice production, but not in the primary symptoms of RLN palsy such as inspiratory stridor.

**Clinical Pearl / High-Yield Fact**
In patients with unilateral RLN palsy, the voice may remain relatively unaffected, whereas breathing difficulties and inspiratory stridor are more prominent. This is due to the cricothyroid muscle maintaining its function, which contributes to voice production.

**Correct Answer:** B. The cricothyroid muscle is usually spared in unilateral Recurrent Laryngeal Nerve palsy.