Which nerve is responsible for swallowing and taste from the posterior tongue?

The glossopharyngeal nerve is primarily responsible for the sensation of taste from the posterior third of the tongue and also plays a crucial role in the swallowing reflex. This nerve is important for relaying taste information from the lingual region it's associated with, and it innervates the muscles involved in swallowing, contributing to the overall process of digestion and the gag reflex. Its role in maintaining the function of the pharynx is essential for both taste and the mechanics of swallowing.

The other nerves listed do serve various functions but do not encompass the specific responsibilities related to the posterior tongue for swallowing and taste. For example, the trigeminal nerve is predominantly involved in sensation for the anterior two-thirds of the tongue. The facial nerve is associated with taste from the anterior part of the tongue and other facial expressions but does not contribute to the posterior portion. The hypoglossal nerve primarily controls tongue movements rather than taste and swallowing. Each of these nerves has distinct functions, making the glossopharyngeal nerve the correct choice for these particular tasks.