In which condition is a shape-based illusion possible?

When shapes and negative spaces show two alternative forms to the viewer

A shape-based illusion occurs when the arrangement of figures, boundaries, and surrounding negative spaces allows perception to shift between two possible readings. The eye may first identify one figure and then notice another figure formed by the background or by the shared edge. This is an application of figure-ground organization and perceptual ambiguity. Therefore, option A is correct because it includes both related shapes and negative space that support alternative forms. Option B and option C remove the visual cues needed for an illusion, while option D lacks the relationship that makes a second interpretation possible. The key is not merely having shapes, but arranging them so perception can change.

This is a Class 9 Art Education question. Chapter: Elements of Art. Topic: Shape.