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阅读下面的短文。每篇短文的后面有五个问题，每个问题有四个备选答案。请根据短文的内容选择最佳答案。每个试题计3分,共计15分。 Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia2 and the Marine Biological Laboratory in WoodsHole3，Mass.4，have invented a backpack that makes electricity from energyproduced while its wearer walks. In military actions，search-and-rescueoperations，and scientific field studies，people rely increasingly on cellphones，global positioning system 5 receivers，night-vision goggles，andother battery powered devices to get around and do their work. The backpackselectricity- generating feature could dramatically reduce the amount of awearers load now devoted to spare batteries，report Rome and his colleagues inthe Sept.9 Science6. Unexpectedly，tests showedthat wearers of the new backpack alter their gaits in response to the packsoscillations，so that they carry loads more comfortably and with less effortthan they do ordinary backpacks. Because of that surprising advantage，Rome plans to commercialize both electric and non-electric versionsof the backpack. 词汇: backpackn.背包 wattn.瓦(特) night-visiongoggle 夜视镜 oscillationn.摆动 verticaladj.垂直的 mountaineern.登山运动员5rEutEri p 练习： | 
