**Core Concept**
The tensors of the vocal cords are muscles responsible for regulating vocal cord tension, which is crucial for speech and singing. The primary muscle involved in this function is the **cricothyroid muscle**. This muscle plays a key role in adjusting the pitch of the voice.

**Why the Correct Answer is Right**
The **cricothyroid muscle** is the only intrinsic laryngeal muscle that is innervated by the **external branch of the superior laryngeal nerve**. It acts to increase the tension of the vocal cords, thereby raising the pitch of the voice. This is achieved by tilting the thyroid cartilage forward, which stretches and lengthens the vocal cords.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the **thyroarytenoid muscle** is involved in relaxing the vocal cords, not tensing them.
**Option B:** This option is incorrect because the **lateral cricoarytenoid muscle** is primarily involved in adducting the vocal cords.
**Option D:** This option is incorrect because the **interarytenoid muscle** is involved in closing the posterior part of the rima glottidis.

**Clinical Pearl / High-Yield Fact**
The function of the **cricothyroid muscle** is critical in voice production, and its dysfunction can lead to voice disorders. Remembering the specific role of this muscle can help in diagnosing and managing voice-related pathologies.

**Correct Answer:** C. Crictothyroid muscle