I. 阅读理解（共10小题每小题2分，满分20分）
阅读下列短文，从每题所给的四个选项（A、B、C和D）中选出最佳选项，并在答题卡上将该项涂黑。
A
Imagine having an idea，drawing it on paper，bringing it to a store and seeing it turned into a physical object．This is now possible with the help of 3D printers．Such machines were once used just by universities and big companies，but now，stores with 3D printing services are appearing around the United States．
