Which AM technology is specifically designed to work with polymers in a layer-by-layer fashion?

Stereolithography is the correct answer because it is a well-established additive manufacturing technology that operates using a layer-by-layer approach specifically with photopolymer resins. In stereolithography, a UV laser is directed onto a vat of liquid resin, curing it into solid layers to create a three-dimensional object. This method utilizes the unique properties of polymers that can be hardened by exposure to light, allowing for the production of complex geometries with high resolution and smooth surface finishes.

While the other options also represent additive manufacturing technologies, they are not specifically designed for polymer processing. Selective laser melting and electron beam melting are focused on processing metals by melting powdered material, which requires different mechanisms and equipment. Direct ink writing could work with polymers, but it generally refers to a broader range of materials and processes, not exclusively to the layer-by-layer polymer-specific methodology that stereolithography employs.