Which technique creates tone by varying the density of small dots?

Correct answer: Stippling

The governing technique is stippling, in which an image is built from separate dots. Increasing the number or density of dots in an area makes that area appear darker, while leaving more space between dots creates a lighter value. Thus option A is correct. Smudging blends graphite, blind contour records an outline without looking at the paper, and burnishing presses or polishes marks rather than using dot density.