## **Core Concept**
The development of the tongue involves multiple embryological structures. The tongue is primarily derived from the first and third pharyngeal arches, with different parts of the tongue originating from distinct embryological sources.

## **Why the Correct Answer is Right**
The posterior one-third of the tongue develops from the **third pharyngeal arch**. This part of the tongue is crucial for swallowing and is innervated by the glossopharyngeal nerve (cranial nerve IX), which is associated with the third pharyngeal arch. The development of the tongue's posterior part from the third arch explains its innervation and function.

## **Why Each Wrong Option is Incorrect**
* **Option A:** The first pharyngeal arch primarily contributes to the development of the anterior two-thirds of the tongue, not the posterior one-third. This part is innervated by the lingual nerve (a branch of the mandibular division of the trigeminal nerve) and the chorda tympani (from the facial nerve).
* **Option B:** While the second pharyngeal arch (hyoid arch) contributes to the development of some structures in the head and neck, it is not directly involved in the formation of the posterior one-third of the tongue.
* **Option D:** The fourth and sixth pharyngeal arches contribute to laryngeal development and are not primarily involved in the formation of the tongue.

## **Clinical Pearl / High-Yield Fact**
A key clinical correlation is that the posterior one-third of the tongue, derived from the third pharyngeal arch, is innervated by the glossopharyngeal nerve (CN IX). This is important for understanding the sensory innervation of the tongue and can be relevant in clinical scenarios involving nerve injuries or lesions affecting the tongue.

## **Correct Answer:** .