五、阅读对话，回答问题。(共 4 小题；第 41—43 小题每小题 2 分，第 44 小题 3 分，满分 9 分)
阅读下面一段对话，用英语回答对话后的问题。
Two friends, Lucas Lu and Sara Wang, are sitting in a cafe.
Lucas: (Reading on his phone. ) Have you heard? China’s skill of building wooden arch bridges(拱桥) is now on the list of UNESCO Intangible Cultural Heritage(非物质文化遗产).
Sara: Really? Are these bridges still there?
Lucas: (Searching on his phone. ) Yes, there are more than 100 of them. Most are in Zhejiang and Fujian.
Sara: But if they are very old bridges, how can they still be there? I mean, shouldn’t they be falling down or even long gone?
Lucas: Well, I think it’s because of the skill of their “mortise and tenon” structure(榫卯结构). Ancient people built these bridges without using nails(钉子). Basically, builders use mortise and tenon joints to fit two sets of beams(梁) together. The longer beams are as long as the main body of the bridge. Mortises are cut into their ends. The shorter beams have tenons at their ends. The tenons are carefully fit into the mortises. Then the beams form a solid arch to support the bridge.
Sara: That sounds like a very difficult skill.
Lucas: It certainly is. And when designing a wooden arch bridge, designers have to think about a lot of things, such as traffic flow and *fengshui*. They must also find out about the area’s land and soil.
Sara: It’s a lot more than just getting from one place to another.
Lucas: Exactly! In fact, the skill has been passed down since the Song dynasty. But modern technology has made it seem out of date.
Sara: I hope more people will see it as it’s now on the UNESCO list.
Lucas: Me too! It would be sad if we lost this ancient wisdom.
41. What is the most amazing and challenging skill in building these ancient bridges?

42. What things do builders have to consider when designing these bridges? Please name two things.

43. When did people first use this skill to build things?

44. 新考法 开放性设问 As a Chinese teenager, how would you help protect this skill?