题目内容：

    Chris Mazdzer won a silver medal in a men’s luge (无舵雪橇) singles event at 2018 Pyeongchang Winter Olympics, South Korea — equaling the best finish ever for any member of the US Olympic luge team. In the luge, competitors lie flat, feet first, on a small sled (雪橇). They can travel around an icy track at speeds up to 140 kilometers an hour. The riders control the sled’s speed by changing the position of their feet or by moving their shoulders.

So why did the US luge team win a medal at the Pyeongchang Olympics? Most credit must go to Chris Mazdzer himself. The American said his win was a product of 16 years of preparation and intense training. But another reason for Mazdzer’s success could have been the 3-D printing technology, which his team used to make its equipment.

The term 3-D is short for three dimensional, meaning an object with length, width and height. In 3-D printing, 3-D models are first created as files, or documents, on a computer. The printer then uses a substance (物质) like plastic or metal to create physical objects. The process involves making one layer of material at a time until the objects reach full form.

The US luge team worked with an American company called Stratasys on the designing and manufacturing process for the sleds. First, the company made a scan, or image, of the body of every member of the luge team. Then, 3-D printing technology was used to create tools for making molds (模子) in the shape of Olympians on top of a sled. The process of designing and tooling sled parts is highly complex and can take several weeks. Officials from the US luge team say 3-D printing can greatly simplify the process, speeding up the production of parts.

Jon Owen, says the use of 3-D printing has made the team more competitive. It helps the team “continuously adjust designs and run the sleds on the track much faster than traditional processes,” he said. He added that the technology also provides a way to perfectly fit each rider to the sled, while cutting production time and costs.

1.According to the author, what mainly contributed to Mazdzer’s winning the medal?

A.His own great efforts. B.His using a new technique.

C.The cooperation with his luge team. D.The US Olympic luge team’s encouragement.

2.To make the sleds for the team, what did the company have to do?

A.To create tools for making sled parts.

B.To take some photos of the members first.

C.To create molds according to the members’ bodies.

D.To ask the Olympians to be present for several weeks.

3.From the last paragraph we learn that 3-D printing most probably __________.

A.saves plenty of competitors’ training time

B.helps competitors achieve their full potential

C.requires great skills of riders to fit the track

D.allows riders to change their sleds continuously

4.What is the text mainly about?

A.How 3-D printing usually works.

B.How we take advantage of 3-D printing.

C.How the US luge team performed this year.

D.How 3-D printing helped Team US go for gold.