Which technique is useful for making soft cloud edges with a brush?

Correct answer: Light circular strokes on a damp surface

Soft cloud edges depend on gradual transitions rather than sharp outlines. Light circular strokes on a damp surface distribute the pigment gently and allow the edge to fade into its surroundings, so option C is correct. A hard dry line creates a definite border, heavy pressure deposits too much colour, and square strokes are not suited to rounded, soft cloud forms.