Which of the following concepts involves visual movement achieved through repetition or gradation?

Rhythm in design refers to the visual movement within a composition that is created by repeating specific elements or gradually changing aspects of those elements. This can be seen in floral arrangements where a type of flower is repeated at intervals to lead the eye through the design, or when colors change gradually to create a flowing effect. The rhythm provides a sense of continuity and harmony, guiding the viewer's gaze and creating a dynamic visual experience.

Balance, while also crucial in design, focuses on the distribution of visual weight rather than the concept of movement. Depth would refer to the perception of space in a composition, often created through layering or perspective. Scale pertains to the size of objects in relation to each other, impacting how they are perceived in terms of proportion but not directly influencing movement through repetition or gradation. Thus, rhythm is the concept that specifically captures the movement achieved through these techniques.