**Core Concept**
The lingual nerve is a branch of the mandibular division of the trigeminal nerve that provides sensory innervation to the anterior two-thirds of the tongue. It courses through the floor of the mouth, looping around the submandibular duct to enter the tongue.

**Why the Correct Answer is Right**
The lingual nerve loops around the submandibular duct to avoid mechanical injury and to maintain its integrity as it enters the tongue. This anatomical arrangement allows the lingual nerve to provide vital sensory input to the anterior tongue, facilitating functions such as taste, temperature, and texture perception. The looping of the lingual nerve around the submandibular duct is a critical anatomical relationship that surgeons and clinicians must appreciate to avoid nerve damage during procedures in the floor of the mouth.

**Why Each Wrong Option is Incorrect**
**Option A:** The mandibular nerve is the parent nerve of the lingual nerve but does not itself loop around the submandibular duct. It provides motor innervation to the muscles of mastication and sensory innervation to the lower lip and chin.

**Option C:** The hypoglossal nerve is a motor nerve that provides innervation to the muscles of the tongue, facilitating movements such as protrusion, retraction, and elevation. It does not loop around the submandibular duct.

**Option D:** The recurrent laryngeal nerve is a branch of the vagus nerve that provides sensory and motor innervation to the larynx. It is not related to the submandibular duct or the lingual nerve.

**Clinical Pearl / High-Yield Fact**
The lingual nerve is a common site for injury during procedures in the floor of the mouth, such as dental extractions and submandibular gland surgery. Clinicians must carefully identify and preserve the lingual nerve to avoid postoperative neuropathic pain and dysfunction.

**✓ Correct Answer: B. Lingual nerve**