Why is gradual direction change useful in showing movement through line?

Correct answer: It guides the viewer’s eye along a smooth, flowing path

Direct answer: D, because gradual direction change guides the viewer’s eye along a smooth, flowing path. When a line turns progressively rather than stopping or changing abruptly, the eye naturally follows its route. This creates a sense of continuity, rhythm, and movement, even though the artwork itself is still. A refers mainly to outlining and does not explain the visual experience of motion. B is incorrect because direction changes do not make a surface uniformly flat. C concerns colour intensity, not the movement created by line. Memory cue: a smoothly turning line gives the eye a road to travel; sudden breaks interrupt that journey.