What is a controlled way to turn a hard acrylic colour boundary into a gradual transition?

Correct answer: Create measured intermediate colours or values and blend them in small sections

The governing technique is controlled gradation through intermediate steps. If the two end colours are mixed directly, the transition may become abrupt or muddy. Preparing measured intermediate hues or values and placing them in small adjacent sections creates a predictable sequence, so option C is correct. A black line emphasizes the boundary, drying prevents blending, and flooding with water is unreliable for acrylic paint.