How should an upper transparent layer be adjusted if the lower colour affects it too strongly?

Correct answer: Slightly increase upper pigment while keeping the layer thin and controlled

The governing concept is controlled transparent layering, often called a glaze. If the lower colour dominates, a small increase in pigment strengthens the upper hue, while keeping the layer thin preserves transparency and allows a controlled interaction between layers. Adding only water would make the upper colour weaker, rubbing the lower layer could damage it, and opaque black would destroy the intended colour relationship. Thus, option A is correct.