The answer is "c. Modeling".
"Modeling" is the use of value to create the illusion of depth.
Numerous artists (however not all) are occupied with making two-dimensional works of art (a flat canvas, for instance) look three-dimensional, particularly when they are delineating items and scenes from this present reality. It's conceivable to make a persuading illusion regarding a three-dimensional pictorial space on a flat surface by utilizing different strategies. Modeling is one of those techniques.