B Though 3D printing technology has been available for over two decades , it has not gone mainstream as hoped because of the high cost and slow print speed.But that may change soon , thanks to German sportswear manufacturer Adidas.On December 15,2016 , the company revealed Adidas 3D Runners , stylish sports sneakers featuring a 3D printed midsole ( 鞋底夹层 ) that provides athletes with the extra cushioning ( 软垫 ) needed for optimal performance. Unlike traditional midsoles , these are not a uniform foam ( 泡沫 ) , but web­like structures with varied density to take into account the impact areas of the foot.This means that the mesh ( 网眼 ) is thicker in the shoe's front and back , both of which hit the ground hard when the athlete runs.A 3D­printed heel , put into the midsole , eliminates the need for traditional gluing or stitching ( 缝合 ) . The shoe upper , made of Primeknit , allows for increased flexibility , stability , and protection in the impact areas. Not surprisingly , the stylish , limited edition black training shoes that were only available for sale in New York City , London , and Tokyo and cost $333 , were an instant hit and sold out within hours of their release.Though not affordable or available to the mass market , the radical shoes are an encouraging step in the right direction for more widespread use of the technology. While printing 3D objects may sound complicated , the process is relatively straightforward.Once the design is downloaded to a printer , a laser creates a layer of material , usually plastic or metal.Successive layers are deposited above one another and fused together until the product is complete.The technology can be used to build everything , from shoe soles to a microwave oven.There is currently even an effort underway to make a printer that is large enough to create the cement layers required to build a house. 24 . 3D printed midsoles are different from ordinary ones in that ________. A . they are made of uniform foam B . they are held together with glue C . the meshes are larger than ordinary ones D . they are like webs with different density 25 . The underlined word “eliminate” in Paragraph 2 most probably means “________” . A . catch up with B . get related to C . be connected with D . get rid of 26 . From Paragraph 3 we can infer that ________. A . the shoes sold well B . the shoes were relatively cheap C . the shoes can satisfy the need of the market D . the company can mass produce the shoes 27 . What does the last paragraph mainly tell us? A . What a 3D printer is. B . How a 3D printer works. C . How complicated the process is. D . What size a 3D printer is.