**Core Concept**
The glottis is the opening between the vocal folds, and its opening and closing are crucial for breathing and speech. The muscles of the larynx, specifically the intrinsic muscles, control the glottis' movement. The intrinsic muscles of the larynx include the cricoarytenoid, arytenoid, and thyroarytenoid muscles.

**Why the Correct Answer is Right**
The posterior cricoarytenoid muscle is the only muscle that abducts (opens) the glottis by rotating the arytenoid cartilages laterally, thereby increasing the space between the vocal folds. This muscle is responsible for opening the glottis during inhalation. The posterior cricoarytenoid muscle is innervated by the recurrent laryngeal nerve, a branch of the vagus nerve.

**Why Each Wrong Option is Incorrect**
**Option A:** The lateral cricoarytenoid muscle adducts (closes) the glottis by rotating the arytenoid cartilages medially, which decreases the space between the vocal folds. It is also innervated by the recurrent laryngeal nerve.
**Option C:** The transverse arytenoid muscle connects the two arytenoid cartilages and helps in the closure of the glottis by bringing the vocal folds together. However, it does not play a significant role in opening the glottis.
**Option D:** The interarytenoid muscle connects the two arytenoid cartilages and helps in the closure of the glottis by bringing the vocal folds together. It is not directly involved in opening the glottis.

**Clinical Pearl / High-Yield Fact**
The posterior cricoarytenoid muscle is the only muscle that opens the glottis, and its paralysis can lead to inspiratory stridor due to the inability to open the glottis during inhalation.

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