Which direction is more suitable for shading a round object?

Correct answer: According to the curvature of the form

The governing concept is form shading, where marks follow the surface so that the drawing communicates volume. On a round object, strokes that follow its curvature help the viewer read its spherical shape, making option A correct. A fixed top-to-bottom direction may flatten the form, random marks reduce structure, and marks outside the contour do not shade the object. Keep the strokes consistent with the imagined surface.