What should an artist do to create both broad and thin lines with the same flat brush?

Correct answer: Use both the broad face and thin edge of the brush

The governing concept is brush orientation: the part of the brush touching the surface determines the mark’s width. Pressing or using the broad face of a flat brush produces a wider line, while turning it so the narrow edge contacts the surface produces a thin line. Option B is correct. Adding water changes flow, not the brush’s basic width, and the other actions are unnecessary or damaging.