What design element primarily forms the shapes of an image?

The correct choice highlights the fundamental role of lines in creating shapes within a design. Lines are the basic building blocks of visual art and design; they have the ability to define the outlines and contours of an image, effectively shaping the objects we see. They can vary in width, length, and character, and can be straight, curved, jagged, or any combination thereof, allowing for a vast range of shapes to be formed.

In design, lines can guide the eye and draw attention to specific areas, but their primary function remains to define shapes. Shapes, in turn, form the foundation of more complex structures and compositions. While other elements like texture, color, and mass contribute to the overall aesthetic and feel of a design, they are secondary to the role lines play in defining the shapes that are critical to any visual representation.