Which cranial nerve is responsible for shoulder elevation?

The accessory nerve (CN XI) is responsible for shoulder elevation due to its primary role in innervating the sternocleidomastoid and trapezius muscles. These muscles are pivotal for movements such as shoulder shrugging and head rotation. The trapezius, in particular, helps elevate the scapula, thereby contributing to the elevation of the shoulder.

In contrast, the other cranial nerves listed serve different functions. The facial nerve (CN VII) primarily innervates the muscles of facial expression, not shoulder movement. The trigeminal nerve (CN V) is mainly responsible for sensation in the face and motor functions such as chewing. The hypoglossal nerve (CN XII) controls the muscles of the tongue, having no role in shoulder elevation. Thus, the accessory nerve is the correct choice given its direct involvement in movements that elevate the shoulder.