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The accessory nerve, also known as cranial nerve XI, is crucial for controlling specific muscles responsible for the movement of the shoulders. This nerve innervates the sternocleidomastoid and trapezius muscles, which facilitate shoulder elevation and allow for shrugging. When the muscles are activated, they help lift and stabilize the shoulders, making the accessory nerve essential for this action.

Recognizing the roles of other cranial nerves can provide clarity. The hypoglossal nerve primarily controls tongue movements and is not involved in shoulder motion. The vagus nerve has a broad influence over various autonomic functions of the body, including heart rate and digestion, but does not impact shoulder movements. The auditory nerve is specifically responsible for hearing and balance, with no connection to muscle movement. Therefore, the accessory nerve is the only one among the options that directly contributes to shrugging the shoulders.