【正确答案】
C
【答案解析】[听力原文] Located at the NASA research center in Iowa, there is a 5,000 gallon container of water. And inside the tank is an underwater treadwheel designed by Davan Newman, an aerospace engineer. For four years, Newman observed divers as they simulated walking on the moon and on Mars on her underwater moving belt. She wanted to discover how the gravity of the moon and of Mars would affect human movement. To do this, Newman attached weights to the divers and then lowered them into the tank and onto the treadwheel. These weights were carefully adjusted so that the divers could experience underwater the gravity of the moon and of Mars as they walked on the treadwheel. Newman concluded that walking on Mars will probably be easier than walking on the moon. The moon has less gravity than Mars does. So at lunar gravity the divers struggled to keep their balance and walked awkwardly. But at Martian gravity, the divers had greater traction and stability and could easily adjust to a pace of 1.5 miles per hour. As Newman gradually increased the speed of the treadwheel, the divers took longer, graceful strides until they comfortably settled into an even quicker pace. Newman also noted that at Martian gravity, the divers needed less oxygen. The data Newman collected will help in the future design of Martian spacesuits. Compare to lunar spacesuits, Martian spacesuits will require smaller air tanks. And to allow for freer movement, the elbow and knee areas of the spacesuits will also be altered. What did Newman change so that the divers could experience different gravity levels? 快速浏览本部分所有选项，由其中的关键词walking on Mars、walking on the Moon、Martian spacesuits等可大致推断，录音内容很可能与太空活动及太空服有关，因此需要重点关注相关内容。 1.三项提到了水(water)或潜水员(diver)，本题可能跟水有关。 2.四项各表示一个因素。 结论：本题考查与水有关的一个因素。 录音开头提到了一个水下踏车，纽曼用它来观察模仿在月球和火星行走的潜水员。纽曼想发现月球和火星的引力如何影响人类行动。当潜水员在水下踏车上行走的时候，她通过调整系在潜水员身上的重量来使其感受月球和火星的引力，因此答案为C。