Which rapid-prototyping process utilizes a ultraviolet laser beam to harden liquid plastic?

Stereolithography is the rapid-prototyping process that uses an ultraviolet (UV) laser beam to cure and harden liquid plastic. This technology operates by focusing a laser on the surface of a vat of photopolymer resin, precisely solidifying the material layer by layer to create a three-dimensional object. This method is particularly effective for producing highly detailed and intricate designs due to the accuracy of the laser and the photopolymer's ability to capture fine features.

In contrast, fused deposition modeling involves the extrusion of thermoplastic materials through a heated nozzle which builds up layers by depositing melted filament. Selective laser sintering utilizes a laser to fuse powdered material, typically plastics or metals, into a solid structure by heating it just below its melting point. Binder jetting employs a liquid binder to bond powdered materials, creating the desired object through a layer-by-layer process, but neither of these methods involves the hardening of liquid plastic through UV light.

Therefore, the uniqueness of stereolithography lies in its use of UV lasers to transform a liquid medium into solid forms, making it the correct answer for this question.