Final answer:
A stationary design line in art provides stability and direction to a composition, and determines motion, direction, and energy. Straight lines, whether horizontal, vertical, or diagonal, are visually stable and provide structure.
Step-by-step explanation:
In the context of art, a stationary design line is a guide that provides stability and direction to a composition. It helps determine the motion, direction, and energy in a work of art. Straight lines, whether horizontal, vertical, or diagonal, are visually stable and give structure to a composition.