What art method involves techniques like stippling and crosshatching to create the illusion of form?

The correct answer is shading. Shading refers to the technique in visual art that uses variations in the darkness or lightness of a color to create the illusion of depth and form on a two-dimensional surface. Techniques such as stippling and crosshatching are specific methods of shading.

Stippling involves creating a series of small dots to build texture and tone, while crosshatching consists of drawing closely spaced parallel lines in multiple layers or directions to create darker areas or to suggest shadow. Both methods effectively convey depth and volume, allowing artists to simulate the three-dimensional quality of objects on paper.

The other choices represent different techniques in drawing but do not focus specifically on creating the illusion of form through darkness and light. Blending typically involves smoothing colors together, sketching is primarily about outlining and capturing basic forms quickly, and contour drawing focuses on the edges and outlines of shapes without emphasizing shading techniques.