In which direction should a round object be shaded?

Correct answer: According to the curvature of the form

The governing concept is form-following, or contour shading. On a round object, strokes should curve in a direction that follows the surface, because this reinforces the object’s volume and makes it appear three-dimensional. Therefore, option D is correct. Random strokes can flatten the form, and straight strokes may ignore its curvature unless the object’s structure specifically requires them. The pressure and spacing should still vary to show light and dark.