Which of the following cranial nerves is responsible for the sense of smell?

The olfactory nerve is responsible for the sense of smell, making it the correct choice. It is one of the cranial nerves and is classified as cranial nerve I. The olfactory nerve transmits sensory information from the olfactory epithelium in the nasal cavity to the brain, allowing individuals to perceive odors.

The other options, while associated with sensory functions, are not related to the sense of smell. The optic nerve is involved in vision, relaying visual information from the retina to the brain. The trigeminal nerve primarily handles sensation from the face and motor functions such as biting and chewing. The facial nerve is responsible for facial expressions, taste sensations from the anterior two-thirds of the tongue, and some functions related to salivary glands. Thus, the olfactory nerve is specifically designated for olfactory input, distinguishing it from the roles of the other cranial nerves.