**Core Concept**
A thyroglossal cyst is a congenital anomaly resulting from an abnormal tract or fistula connecting the thyroid gland to the foramen cecum of the tongue. This anomaly occurs due to incomplete closure of the thyroglossal duct during embryonic development.

**Why the Correct Answer is Right**
The most common site of a thyroglossal cyst is at the level of the hyoid bone, where the thyroglossal duct usually obliterates and forms a fibrous band. This is because the duct usually closes at this point, and remnants of the duct can give rise to a cyst. The cyst may be found in the midline, anterior to the hyoid bone, and can be associated with a tract leading to the foramen cecum of the tongue.

**Why Each Wrong Option is Incorrect**
* **Option A:** While the tongue is the origin of the thyroglossal duct, it is not the most common site of a thyroglossal cyst. The duct usually obliterates and forms a fibrous band at the level of the hyoid bone, not the tongue.
* **Option B:** The foramen cecum is the site of origin of the thyroglossal duct, but it is not the most common site of a thyroglossal cyst. The duct usually closes and forms a fibrous band at a lower level, near the hyoid bone.
* **Option D:** The thyroid gland is the normal location of the thyroid tissue, but it is not the most common site of a thyroglossal cyst. Thyroglossal cysts occur as a result of an abnormal tract or fistula connecting the thyroid gland to the foramen cecum of the tongue.

**Clinical Pearl / High-Yield Fact**
A key feature of thyroglossal cysts is their association with a midline neck mass that moves superiorly on protrusion of the tongue. This characteristic movement is due to the tract connecting the cyst to the foramen cecum of the tongue.

**Correct Answer:** C.