Which of the following is a major muscle of the back?

The trapezius muscle is considered a major muscle of the back because of its size, location, and functions. It spans across the upper back and neck region, resembling a large triangle or trapezoid shape. This muscle plays a crucial role in various movements and postures of the shoulder girdle, including the retraction, elevation, and depression of the scapula. It also assists in stabilizing and rotating the shoulder blade, as well as extending and laterally flexing the neck. The trapezius muscle is highly visible and easily palpable, making it a significant anatomical landmark in the study of the back musculature.