What can be a major cause of unwanted brush marks in a transparent colour layer?

Correct answer: Uneven paint consistency and repeated brushing

In a transparent layer, the governing concept is an even film of paint with economical handling. If the mixture has uneven consistency, some areas deposit more pigment than others; repeated brushing then redistributes or lifts the layer and leaves streaks. Option B is correct. A colour name, paper shape, or wooden handle has no direct mechanical effect on the uniformity of the transparent paint film.