Why is rough watercolour paper useful for dry-brush texture?

Correct answer: Its raised surface catches paint while the lower areas remain white

Dry-brush texture depends on using a brush containing limited water and pigment. Rough paper has raised fibres and shallow depressions; the raised areas catch the paint, while the lower parts are not fully reached. This creates broken, grainy marks that can suggest stone, wood, grass, or a rough wall. Paper roughness does not itself make pigment more transparent, erase every mark, or harden the brush. Therefore, option C correctly explains the effect.