What is useful for showing roundness in a cylinder?

Correct answer: Shading and curved line

The direct answer is C: shading and a curved line. A cylinder has a curved side and usually circular or oval ends. To show it convincingly in a drawing, the artist uses curved outlines and changes in light and dark. The reasoning is: the curved line suggests the rounded boundary; shading shows where light falls and where the surface turns away; together they create the appearance of a three-dimensional cylinder. Option A, drawing only a square, gives a flat angular shape and does not show the cylinder’s curved surface. Option B, folding paper, changes a real object but does not itself draw or represent roundness in a flat picture. Option C is correct because curved lines and shading communicate form, volume, and depth. Option D, only red colour, may colour the object but cannot by itself explain its rounded form. Memory cue: curved outline plus light-and-dark shading shows cylindrical form.