If a poster-colour surface feels uneven after drying what is the most likely cause?

Correct answer: Paint had pooled or the layer thickness was uneven

The governing concept is surface control during application. If excess paint collects in one area or the coating is thicker in some places, drying can leave raised or uneven areas that are felt by touch. Thus option D is correct. A good colour scheme concerns design, clean paper generally helps application, and a new brush is not itself a cause of texture. Controlling brush load and spreading an even layer prevents the problem.