**Core Concept**
The patient's complaint of a "lump in the throat" without difficulty in swallowing suggests a condition affecting the larynx or pharynx, but not the esophagus. This symptom is often associated with the involuntary contraction of a specific muscle in the neck.

**Why the Correct Answer is Right**
The muscle responsible for this symptom is the **Cricothyroid muscle**. It is a thin, fan-shaped muscle that lies superficial to the cricothyroid joint and is involved in the regulation of pitch during phonation. The cricothyroid muscle is innervated by the external branch of the superior laryngeal nerve. When this muscle contracts involuntarily, it can cause a sensation of a "lump in the throat" or a feeling of tightness in the neck, even if swallowing is unaffected.

**Why Each Wrong Option is Incorrect**
* **Option A:** The Thyrohyoid muscle is involved in the elevation of the larynx and is not typically associated with the sensation of a lump in the throat.
* **Option B:** The Lateral cricoarytenoid muscle is involved in the adduction of the vocal folds and is not typically associated with the sensation of a lump in the throat.
* **Option C:** The Posterior cricoarytenoid muscle is involved in the abduction of the vocal folds and is not typically associated with the sensation of a lump in the throat.

**Clinical Pearl / High-Yield Fact**
The cricothyroid muscle can be a source of difficulty in phonation, particularly in patients with thyroid or cricothyroid cartilage abnormalities. Clinicians should consider the cricothyroid muscle when evaluating patients with voice or swallowing complaints.

**Correct Answer: C. Posterior cricoarytenoid muscle**