**Core Concept**
The larynx, or voice box, contains various skeletal muscles that control its movements. These muscles can be broadly categorized into intrinsic and extrinsic muscles. Intrinsic muscles are responsible for opening, closing, and adjusting the tension of the glottis, which is the space between the vocal folds.

**Why the Correct Answer is Right**
The posterior cricoarytenoid muscle is the only muscle that abducts the vocal folds, thereby opening the glottis. It achieves this by pulling on the arytenoid cartilages, which are located at the top of the vocal folds. The posterior cricoarytenoid muscle is innervated by the recurrent laryngeal nerve, a branch of the vagus nerve. This muscle plays a crucial role in maintaining airway patency, especially during inspiration.

**Why Each Wrong Option is Incorrect**
**Option A:** The lateral cricoarytenoid muscle adducts the vocal folds, closing the glottis, not opening it.

**Option C:** The transverse arytenoid muscle connects the two arytenoid cartilages and helps to close the glottis during swallowing.

**Option D:** The interarytenoid muscle is a transverse muscle that connects the two arytenoid cartilages and also helps to close the glottis during swallowing.

**Clinical Pearl / High-Yield Fact**
The posterior cricoarytenoid muscle is the only muscle that opens the glottis, and its paralysis can lead to vocal fold fixation and respiratory distress.

**Correct Answer:**
✓ Correct Answer: B. Posterior cricoarytenoid