請依下文回答第 44 題到第 48 題 Additive Manufacturing, or 3D printing, is known as it builds things through an additive process. It has a numberof advantages over traditional techniques. Instead of machining components from solid billets of raw metal, a processin which much of the metal may be cut away and thus wasted, only the material needed to create the part is used in 3Dprinting. The technology can also be used to make prototypes and items that are too complicated to be machined.Meanwhile, existing objects can be scanned, reverse engineered and then “reprinted.” Another major advantage is thatas there is no need to retool equipment each time product specifications are changed, 3D printers are ideal for customjobs and short production runs. All that needs to be done is to make alterations to the program that controls the printheads. With all those advantages, some experts believe that the technology will overturn many of the traditionaleconomics of production, as unit labor costs and traditional economics of scale are not applicable. The technologyunderlying 3D printing can be traced back to the 1970s, when the inkjet printer was invented. The mid-1980s saw theinkjet concept adapted to enable printing with materials other than ink. For years, however, the materials used to printobjects were not robust enough to create a working prototype. The end product did not have enough structuralintegrity to serve as anything more than a visual reference for engineers creating products with computer aided design(CAD). The big breakthrough of 3D printing took place in the early 2000s, when companies and researchers starteddeveloping stronger plastic blends and began to use laser technology that not only allowed the use of powdered metalsas the “ink,” but also improved the accuracy and efficiency of 3D printers. Today, the materials used to print objectsrange from numerous plastics and ceramics to metals and rubber-like substances. Somehow, the development of 3Dprinting is similar to that of photocopying. As with photocopiers, 3D printers are becoming more affordable, moreapplications for them are being found and more people are recognizing that the new technology can make thingseasier. The biggest ambition of those in the trade, therefore, is to see 3D printing become as commonplace asphotocopying. Hopefully, people might be able to purchase a digital file of a 3D object, push the “print” button, andenjoy their designer product soon afterward.
【題組】44 Which of the following defines the word “additive” in the first sentence?
(A) A substance that is added to food in order to improve its flavor.
(B) A factor that is added to other factors for better overall effects.
(C) A process that builds things by adding materials layer by layer.
(D) A way that builds tension by adding materials again and again.
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