If poster-colour letters have jagged edges after drying, what is the most likely cause?

Correct answer: The bristles were splayed or stroke control was weak

Clean lettering requires a pointed, well-controlled brush and steady movement along the intended boundary. Splayed bristles deposit paint outside the planned line, while weak stroke control produces irregular edges that remain visible after drying. Thus option C is correct. Bright colour, a dry background, or large letters may affect appearance or scale, but they do not most directly create jagged edges.