How can the light area be kept clean while blending from a dark colour toward a light colour?

Correct answer: Clean the brush at each stage and gradually reduce the dark paint

The governing principle is pigment control during a dark-to-light gradient. Dark pigment should be reduced progressively rather than dragged into the clean light area. Cleaning or rinsing the brush between stages prevents accumulated pigment from contaminating the highlight, while a separate middle mixture can soften the transition. Option A combines both protections. Direct dragging, flooding with water, or adding black would dirty or weaken the light region.