**Core Concept**
The **pyriform fossa** is a part of the hypopharynx, and malignant lesions in this area can cause referred pain due to the complex innervation of the head and neck region. The **cranial nerves**, particularly those involved in sensory innervation, play a crucial role in the referral of pain.

**Why the Correct Answer is Right**
The correct answer involves the **Glossopharyngeal nerve (CN IX)**, which provides sensory innervation to the pharynx, including the pyriform fossa, and also has a branch that innervates the ear. This dual innervation allows for the referral of pain from the pyriform fossa to the ear. The **Jacobson's nerve**, a branch of CN IX, is specifically involved in this sensory pathway.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not accurately describe the nerve responsible for referring pain from the pyriform fossa to the ear.
**Option B:** Incorrect as it is not the primary nerve involved in the sensory innervation of the pyriform fossa and the ear.
**Option C:** Incorrect because, although involved in sensory innervation of the face, it is not directly responsible for the referral of pain from the pyriform fossa to the ear.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the **Glossopharyngeal nerve** is involved in the innervation of both the pharynx and the ear, making it a critical nerve in understanding the referral of pain in head and neck malignancies.

**Correct Answer:** D. Glossopharyngeal nerve.