**Core Concept**
The sympathetic root of the otic ganglion is a crucial component of the parasympathetic nervous system, specifically the facial nerve's (cranial nerve VII) branch to the parotid gland. This root is formed by a branch from the internal carotid plexus, which provides sympathetic innervation to the parotid gland.

**Why the Correct Answer is Right**
The sympathetic root of the otic ganglion is formed by a branch from the internal carotid plexus, which contains postganglionic sympathetic fibers. These fibers arise from the superior cervical ganglion and provide sympathetic innervation to the parotid gland. The parasympathetic root, on the other hand, is formed by the auriculotemporal nerve, which carries preganglionic parasympathetic fibers from the glossopharyngeal nerve (cranial nerve IX). The sympathetic root and the parasympathetic root of the otic ganglion synapse in the ganglion, with the postganglionic parasympathetic fibers then traveling to the parotid gland to stimulate salivation.

**Why Each Wrong Option is Incorrect**
**Option A:** Not applicable (no information provided).
**Option B:** Incorrect, as it does not specify the correct origin of the sympathetic root of the otic ganglion.
**Option C:** Incorrect, as it does not accurately describe the sympathetic root of the otic ganglion.
**Option D:** Incorrect, as it does not specify the correct origin of the sympathetic root of the otic ganglion.

**Clinical Pearl / High-Yield Fact**
The otic ganglion plays a crucial role in the innervation of the parotid gland, and understanding the sympathetic and parasympathetic roots of the ganglion is essential for appreciating the complex interplay between the autonomic nervous system and salivation. The parasympathetic root of the otic ganglion is often tested on exams, but the sympathetic root is equally important for a comprehensive understanding of the autonomic nervous system.

**Correct Answer: B. The internal carotid plexus.**