A patient in the emergency room has been stabbed in the back of the neck and complains that he is unable to lift his shoulder. Which of the following nerves has likely been damaged?

The trapezius muscle has an extensive attachment to the occipital bone, the ligamentum nuchae, the spinous processes, and supraspinous ligaments down to T12, the spine of the scapula, the acromion, and the lateral third of the clavicle. Such a fan-shaped muscle has many actions. The upper and middle fibers, which attach to the clavicle and acromion, lift the point of the shoulder. The trapezius is innervated by the accessory nerve, and the ability to "shrug" the shoulder is often used to test the function of the accessory nerve.