## **Core Concept**
The question tests knowledge of laryngeal muscles and their functions, specifically regarding vocal cord movement. The **abductor of the vocal cords** is the muscle responsible for opening or separating the vocal cords, which is crucial for breathing and voice modulation.

## **Why the Correct Answer is Right**
The correct answer, **Posterior Cricoarytenoid muscle**, is the only muscle that abducts the vocal cords. This muscle originates from the posterior surface of the cricoid cartilage and inserts into the arytenoid cartilages. When it contracts, it causes the arytenoid cartilages to rotate outward, which in turn causes the vocal cords to abduct or move apart. This action is essential for preventing food and water from entering the trachea during swallowing and for regulating airflow during breathing.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The **Thyroarytenoid muscle** primarily adducts the vocal cords and helps in adjusting the tension of the vocal cords, not abduction.
- **Option B:** The **Lateral Cricoarytenoid muscle** also adducts the vocal cords and helps in adjusting their tension but does not abduct them.
- **Option D:** The **Interarytenoid muscle** helps to close the posterior part of the rima glottidis 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 muscle that can open (abduct) the glottis. This is crucial during procedures like endotracheal intubation or in conditions where vocal cord abduction is necessary for airway management. Damage to the recurrent laryngeal nerve, which supplies this muscle, can lead to vocal cord paralysis and potentially life-threatening airway obstruction.

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