**Core Concept**
The question is testing the student's knowledge of the laryngeal muscles, specifically their functions and innervations. **The posterior cricoarytenoid muscle is the only muscle that abducts the vocal cords, whereas the muscles that adduct the vocal cords are the arytenoid muscles (specifically, the lateral and transverse arytenoid muscles) and the cricothyroid muscle, which also adducts and tens the vocal cords.**

**Why the Correct Answer is Right**
The muscles that adduct the vocal cords are responsible for bringing the vocal folds together, which increases the tension and pitch of the voice. The **lateral arytenoid muscle** and **transverse arytenoid muscle** are the primary muscles responsible for adduction of the vocal cords, while the **cricothyroid muscle** also contributes to adduction and tension of the vocal cords. These muscles work in concert to control the pitch and volume of the voice.

**Why Each Wrong Option is Incorrect**
* **Option A:** The posterior cricoarytenoid muscle, as mentioned earlier, is responsible for abduction of the vocal cords, not adduction.
* **Option B:** The thyroarytenoid muscle is involved in relaxation of the vocal cords, not adduction.
* **Option C:** The cricopharyngeus muscle is involved in the pharyngeal sphincter and not directly involved in vocal cord adduction.

**Clinical Pearl / High-Yield Fact**
The arytenoid muscles (lateral and transverse) are innervated by the recurrent laryngeal nerve, which is a branch of the vagus nerve. Damage to this nerve can result in vocal cord paralysis, leading to hoarseness or loss of voice.

**Correct Answer:** D.