Three-dimensional (3D) printing has opened up a world of new possibilities. Thanks to this new technology, it’s possible to print just about anything you can name. Unfortunately, this means that although 3D printers can be put to good use, they can be used to make harmful things as well. One of the uses people in the United States, in particular, have found for 3D printers is to use them for printing guns. A number of people have created templates for various gun parts, and uploaded them to the Internet. If a person buys a gun from a shop, that gun has a serial number, which means the gun can be tracked. A gun that is printed at home, however, has no serial number, and thus no way of being tracked. Some states, such as California, have passed laws requiring people who print a gun to apply for a serial number, but the law is easy to ignore. In the US, it is actually illegal to print a gun that cannot be detected by a metal detector. This would make a gun easy to sneak past security at airports and other public places. So, for printed guns to be legal, they have to have a metal plate in them. What is the number of 3D-printed guns out there? It’s hard to say. When printable gun plans were first put online, they were downloaded about 100,000 times. At that time, only about 20 percent of the downloaders had 3D printers capable of making a gun. But how those numbers have expanded since then is anybody’s guess. Why are printed guns a problem, according to the article? a. The often malfunction. b. They are too effective. c. They can be hard to track. d. They are really cheap to make. 2. For a 3D-printed gun to be legal, which of the following must take place? a. It must have the serial number removed. b. It must have metal in it. c. It should be printed under police supervision. d. It must be 100% plastic. 3. According to statistics, how many users could print a gun when plans for them were first put online? a. 2,000 b. 10,000 c. 20,000 d. 100,000 4. How many printed guns exist now, according to the article? a. The amount is known to law enforcement, but not the public. b. The number equals 20 percent of the amount of guns sold. c. They are around 100,000. d. There is no definite answer. 5. Which of the following can be inferred from the article? a.3D printers can be used for good as well as evil。 b.3D printers can do more harm than good。 c.3D printers should be taken off the market。 d.3D printers have yet to prove their worth to society。
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