**Core Concept**
The direct and consensual light reflexes are important oculomotor pathways that allow the eye to respond to light by constricting the pupil. These reflexes are mediated by the afferent and efferent fibers of the oculomotor nerve (cranial nerve III). The afferent fibers originate from the retina, while the efferent fibers originate from the Edinger-Westphal nucleus and synapse in the ciliary ganglion to control pupil constriction.

**Why the Correct Answer is Right**
The oculomotor nerve (cranial nerve III) is responsible for controlling the majority of the extraocular muscles, including the medial rectus, superior rectus, inferior rectus, inferior oblique, and levator palpebrae superioris. Importantly, the oculomotor nerve also carries parasympathetic fibers from the Edinger-Westphal nucleus that synapse in the ciliary ganglion to control pupillary constriction. A lesion of the oculomotor nerve would disrupt these parasympathetic fibers, leading to loss of the direct and consensual light reflexes.

**Why Each Wrong Option is Incorrect**
**Option A:** The trigeminal nerve (cranial nerve V) is primarily responsible for sensory innervation of the face and motor innervation of the muscles of mastication. It is not directly involved in the light reflex pathways.

**Option C:** The trochlear nerve (cranial nerve IV) is responsible for innervating the superior oblique muscle, which is involved in eye movement but not in the light reflex pathways.

**Option D:** The abducens nerve (cranial nerve VI) is responsible for innervating the lateral rectus muscle, which is involved in eye movement but not in the light reflex pathways.

**Clinical Pearl / High-Yield Fact**
Remember that the oculomotor nerve (cranial nerve III) is responsible for controlling pupillary constriction, as well as the majority of the extraocular muscles involved in eye movement. A lesion of this nerve can lead to loss of the direct and consensual light reflexes, as well as ptosis (drooping eyelid) and external ophthalmoplegia (weakness of the extraocular muscles).

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