Which cranial nerve would be affected in a patient who reports having loss the sense of smell?

Anosmia, the loss of olfaction, results from dysfunction of the olfactory nerve, which transmits sensory data from the nasal epithelium. It is the shortest cranial nerve and passes through the cribriform plate of the ethmoid bone. Damage often occurs via head trauma, viral infections, or anterior fossa tumors. A. IX: The glossopharyngeal nerve mediates taste for the posterior third of the tongue and the gag reflex. It provides secretomotor fibers to the parotid gland and visceral sensory input from the carotid sinus. It does not contribute to the sense of smell. B. I: Cranial nerve I is the olfactory nerve, purely responsible for the special visceral afferent pathway of smell. Clinical assessment involves testing each nostril with non-irritating odors like coffee. This nerve is the direct anatomical structure responsible for the patient's symptoms. C. XII: The hypoglossal nerve is a purely motor nerve that innervates the extrinsic and intrinsic muscles of the tongue. Assessment involves observing for tongue deviation, fasciculations, or atrophy during protrusion. It has no sensory function related to olfaction or chemicals. D. X: The vagus nerve provides extensive parasympathetic innervation to the thoracic and abdominal viscera and controls phonation and swallowing. It carries sensory information from the larynx and pharynx. It is not involved in the special sensory process of smelling.