The muscle that extends across the upper back and neck and helps move the shoulder is the trapezius.

• A. Latissimus Dorsi
• B. Trapezius
• C. Deltoid
• D. Rhomboid

Answer: (B)

The trapezius fits the description because it is a large muscle that spans across the upper back and the back of the neck and acts on the shoulder girdle. Its upper fibers elevate the shoulder, its middle fibers retract the shoulder blades toward the spine, and its lower fibers help depress and rotate the scapula so the arm can lift overhead. This combination of actions directly influences shoulder movement, which is why it’s the best choice.

Latissimus dorsi is a back muscle that reaches to the humerus and mainly powers movements of the arm itself (extension, adduction, internal rotation) rather than moving the shoulder girdle. Deltoid sits over the shoulder joint and primarily enables arm lifting away from the body (abduction) and shoulder flexion/extension. Rhomboids retract and slightly elevate the scapula and contribute to shoulder stability, but they don’t extend across the upper back and neck the way the trapezius does.