What effect is generally produced by gradually making the brush more upright during a stroke?

Correct answer: The stroke becomes thinner as surface contact decreases

The governing concept is the relationship between brush angle and contact area. At a flatter angle, many bristles touch the surface and create a wider mark. As the brush gradually becomes upright, fewer bristles make contact, so the stroke tapers and becomes thinner. Option C is correct. The angle does not erase the colour or shorten the bristles, and the stroke does not become wider as contact decreases.