Small white letters painted over a dark base look broken. What is the likely cause?

Correct answer: White paint being too thin and insufficient on the brush

The governing concept is opacity and coverage. White poster colour must form a sufficiently dense film to hide a dark underlayer. If it is over-diluted or the brush carries too little paint, the dark base shows through in gaps, making small letters appear broken. Option A identifies both causes. A completely dry base is normally helpful, a pointed brush can improve small details, and thick paper does not inherently produce broken lettering.