What nerve is responsible for motor control of the tongue?

The nerve responsible for motor control of the tongue is the hypoglossal nerve, which is cranial nerve XII. This nerve innervates most of the intrinsic and extrinsic muscles of the tongue, allowing for movement essential for various functions such as speech, swallowing, and manipulating food during chewing.

Cranial nerve IX, known as the glossopharyngeal nerve, primarily has sensory and some motor functions related to the oropharynx and contributes to taste sensations and salivary gland function, but it does not control tongue movement. Cranial nerve X, or the vagus nerve, also has a range of sensory and motor functions but is primarily involved in autonomic control of the heart and digestive tract, not in tongue movement. Cranial nerve VII, the facial nerve, is mainly responsible for the muscles of facial expression and also has some sensory functions, particularly taste from the anterior part of the tongue, but it does not directly control the motor functions of the tongue itself.

Therefore, cranial nerve XII is the correct answer as it directly commands the muscular movements required for the tongue's functions.