**Core Concept**
The laryngeal muscles play a crucial role in regulating the tension and position of the vocal cords, thereby controlling voice production and respiration. The abductor muscles are responsible for opening the glottis, allowing for inspiration and preventing vocal cord closure.

**Why the Correct Answer is Right**
The posterior cricoarytenoid muscle is the only abductor of the vocal cords. It originates from the posterior surface of the cricoid cartilage and inserts into the muscular process of the arytenoid cartilage. Contraction of this muscle rotates the arytenoid cartilage, resulting in the opening of the glottis and abduction of the vocal cords. This action is essential for inspiration and preventing vocal cord closure during respiration.

**Why Each Wrong Option is Incorrect**
* **Option A:** The thyroarytenoid muscle is an adductor of the vocal cords, not an abductor.
* **Option B:** The cricothyroid muscle is responsible for tension of the vocal cords, but it does not abduct the vocal cords.
* **Option D:** The lateral cricoarytenoid muscle is an adductor of the vocal cords, not an abductor.

**Clinical Pearl / High-Yield Fact**
The posterior cricoarytenoid muscle is the only abductor of the vocal cords, making it essential for maintaining a patent airway during respiration. Damage to this muscle can lead to vocal cord paralysis, resulting in voice changes and respiratory compromise.

**Correct Answer: C. Posterior cricoarytenoid muscle**