## **Core Concept**
The question tests the knowledge of laryngeal muscles and their functions, specifically the muscle responsible for abducting the vocal cords. The larynx contains several intrinsic muscles that control vocal cord movement, including the posterior cricoarytenoid, lateral cricoarytenoid, and thyroarytenoid muscles.

## **Why the Correct Answer is Right**
The correct answer, **Posterior Cricoarytenoid**, is the only muscle that abducts the vocal cords. This muscle is responsible for opening the glottis by rotating the arytenoid cartilages outward, thereby separating the vocal cords. This action is crucial for breathing and preventing food and water from entering the trachea during swallowing.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The **Lateral Cricoarytenoid** muscle adducts the vocal cords and helps to shorten and tense them, not abduct them.
- **Option B:** The **Thyroarytenoid** muscle, also known as the vocalis muscle when specifically referring to the part that acts on the vocal cords, helps to relax the vocal cords and is involved in regulating pitch and volume but does not abduct the vocal cords.
- **Option D:** The **Interarytenoid** muscle, also known as the arytenoid muscle, helps to close the posterior part of the glottis by approximating the arytenoid cartilages but does not abduct the vocal cords.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that the posterior cricoarytenoid muscle is the only abductor of the vocal cords. This is crucial in procedures like endotracheal intubation and in conditions like vocal cord paralysis, where the function of this muscle may be compromised, leading to difficulties in breathing.

## **Correct Answer:** C. Posterior Cricoarytenoid.