What changes when the direction of a brush stroke is changed?

Correct answer: Movement and visual effect of the line

The governing concept is directional brushwork. A stroke moving horizontally, vertically, diagonally, or in a curve can suggest different movement, texture, emphasis, and form, even when the brush and colour remain unchanged. Thus option C is correct because direction affects the line’s movement and visual effect. It does not alter the paper size, the colour’s name, or the brush’s price.