题目内容：

Printing images is easy. Just select an image of a purple robot on your PC, for example, and press print. Your home printer exactly shoots drops of ink onto a flat piece of paper, creating the robot’s 2-D image. “Printing” 3-D objects is different. Take the purple robot. First select a file of the 3-D printer. Immediately, the printer begins making noise, and a nozzle (喷嘴) releases plastic material in thin layers. In two or three hours, a 3-D purple robot is standing before you.

3-D printing has developed to the point where printers can now create high-quality objects using a variety of materials, including metals. That means 3-D printers can now make final products that meet high industrial standards. 3-D printers are already being used to make parts for racecars and jets as well as man-made limbs and hearing aids.

So far, few homes have 3-D printers. That’s because 3-D printing is not only new to most people but also quite expensive. To bring 3-D printing to the masses, some retail stores (零售商店) plan to offer the service. For example, the Staples chain of office supply stores has announced that it will offer 3-D printing in Europe beginning in 2013. Customers will be able to submit their own 3-D designs to Staples website for printing. After the job is done, they’ll pick up their item at a nearby Staples store or have it mailed to their homes. This service is sure to encourage many more people to try out 3-D printing.

1.According to this article, who are 3-D printed parts already helping?

A. People with physical disabilities.

B. People in the solar energy field

C. People who lack suitable housing

D. People in need of computer skills

2.What will customers need in order to submit their designs to Staples?

A. A credit card account

B. Its local phone number

C. Professional experience

D. Access to the Internet

3.What does the writer of this article imply about 3-D printing?

A. Its inventor is famous

B. Its future looks bright.

C. It is still quite cheap.

D. It will be of little use.

4.What do we learn about the 3-D purple robot?

A. How long it can usually last

B. How it can darken its own color

C. How it gradually takes shape

D. How much it costs to produce