Which form mainly has a continuous curved surface?

Sphere

The governing concept is the surface structure of geometric forms. A sphere is a round three-dimensional solid in which every part of the outer surface curves continuously around the centre. It has no flat face, straight edge, or sharp corner, so option A is correct. A cube has separate flat square planes joined by straight edges. A rectangular solid also has flat rectangular faces and angular edges, even though its proportions differ from a cube. A flat square is a two-dimensional plane and therefore does not have a complete three-dimensional curved surface at all. In observational drawing, a sphere is shown with gradual changes of light and shade because its surface turns smoothly away from the light. Recognising this continuous curvature helps an artist choose soft transitions rather than hard plane changes.

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