What should be done to avoid an abrupt colour change in blending?

Correct answer: Create intermediate colour values

A smooth blend is created by reducing the difference between neighbouring colours through intermediate values or transitional tones. These middle steps guide the eye gradually from one colour or shade to the next. Therefore option A is correct. A black line creates a harsh boundary, leaving the area white interrupts the transition, and scratching removes or damages the painted surface rather than blending it.