**Core Concept**
Loss of lacrimation is a condition characterized by the inability to produce tears, leading to dryness and discomfort in the eyes. This condition is often caused by damage to the nerves or glands responsible for tear production.

**Why the Correct Answer is Right**
The correct answer is related to the innervation of the lacrimal gland. The lacrimal gland is primarily innervated by the parasympathetic nervous system, specifically the facial nerve (CN VII) through its greater superficial petrosal nerve branch, which releases acetylcholine to stimulate lacrimation. Injury to the facial nerve can lead to loss of lacrimation.

**Why Each Wrong Option is Incorrect**
* **Option A:** The ophthalmic nerve (V1) is involved in the sensory innervation of the eye, but it is not directly responsible for lacrimation.
* **Option B:** The trigeminal nerve (CN V) is responsible for the motor innervation of the muscles of mastication, but it is not directly involved in lacrimation.
* **Option D:** The sympathetic nervous system can modulate tear production, but it is not the primary pathway for lacrimation.

**Clinical Pearl / High-Yield Fact**
The facial nerve is responsible for the innervation of multiple structures in the face, including the lacrimal gland, the submandibular gland, and the muscles of facial expression. Damage to the facial nerve can result in a range of symptoms, including loss of lacrimation, difficulty swallowing, and facial weakness.

**Correct Answer: C. Facial nerve. The facial nerve is responsible for the innervation of the lacrimal gland.**