Which cranial nerve is primarily involved in taste sensation from the posterior one-third of the tongue?

Cranial nerve IX, known as the Glossopharyngeal nerve, is primarily responsible for taste sensation from the posterior one-third of the tongue. This nerve innervates taste buds located in this region, allowing for the perception of taste.

The glossopharyngeal nerve also has other functions, such as providing sensory innervation to the pharynx and contributing to the gag reflex. Additionally, it plays a role in monitoring blood pressure and blood gases through its innervation of the carotid body and sinus.

While other cranial nerves contribute to taste and sensation in different areas of the mouth and throat, cranial nerve IX is specifically recognized for its role in taste from the posterior part of the tongue, making it the correct choice for this question.