What is the main difference between surfaces of a sphere and a cube?

Sphere surface is curved, cube faces are flat

The governing concept is distinguishing solids by the character of their surfaces, faces, and edges. A sphere has one continuous, smooth, curved surface; it has no flat faces, straight edges, or vertices. A cube has six flat square faces that meet along straight edges and form corners or vertices. Option A is correct because it gives the essential surface contrast. Option B incorrectly assigns cube-like faces to a sphere. Option C is false because edges are a defining feature of a cube, and D ignores the obvious structural difference between the two forms. In drawing, this distinction affects construction and shading: a sphere usually has smoothly changing tones, while a cube often shows clearer changes from one plane to another.

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