What is the simplest way to preserve a highlight in a sketch?

Correct answer: Leave that area light or white

The governing concept is highlight preservation in tonal shading. A highlight is the area receiving the strongest light, so it must remain brighter than the surrounding middle and dark tones. The simplest approach is to use the white of the paper or apply only a very light layer of graphite, making option A correct. Dark shading, heavy outlining, or dense dots would add value to that area and reduce the visible effect of reflected light.