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四川旺苍县2017高考英语阅读理解选练 阅读下列四篇短文，从每小题后所给的A,B,C或D四个选项中，选出最佳选项。 FILTON, just outside Bristol, is where Britain’s fleet of Concorde supersonic（超音速的）airliners was built. There, something remarkable is being created. Little by little a machine is “printing” a complex titanium bracket (钛合金支架), about the size of a shoe, which normally would have to be cut from a solid block of metal. Brackets are only the beginning. The researchers at Filton have a much bigger ambition: to print the entire wing of an airliner. Unrealistic as this may seem, many other people are using 3D printing technology to create similarly remarkable things. These include medical implants, jewellery, football boots designed for individual feet, lampshades, racing-car parts, solid-state batteries and customized mobile phones. Some are even making mechanical devices (仪器). At the Massachusetts Institute of Technology (MIT), Peter Schmitt, a PhD student, has been printing something that is like the workings of a grandfather clock. It took him a few attempts to get right, but eventually he removed the plastic clock from a 3D printer, hung it on the wall and pulled down the counterweight. It started ticking. Engineers and designers have been using 3D printers for more than a decade, but mostly to make original types quickly and cheaply before they embark on the expensive business of tooling up a factory to produce the real thing. As 3D printers have become more able to work with a broader range of materials, including production-grade plastics and metals, the machines are increasingly being used to make final products too. More than 20% of the output of 3D printers is now final products rather than original types, according to Terry Wohlers, who runs a research firm specializing in the field. He predicts that this will rise to 50% by 2020. | 
