ElectricBackpack
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.
练习：
A they can be verylarge.
C your handsare freed to do other things.
2. What is the most important feature of the backpack invented byLawrence C.Rome
A It produces electricity forelectronic devices while the wearer walks.
C It is small andconvenient.
3. The word springs inParagraph 3 means
B the season of the year，occurring between winter and summer.
D a length of metal woundaround，which returns to its original shape after
4. According to Paragraph 4，what does Rome plan to do?
B To put the backpack on the market.
D To promote the backpack in anewspaper or on television.
ways before crossing the street!?
B Enjoyingelectronic devices while walking may invite traffic accidents.
D It is wise of you to have such abackpack.
C第一段告诉我们，因为背包可以装许多东西，所以可以将双手解放出来做其他事情：tofree your hands to do other things。
D springs在此是弹簧的意思。spring是一个多义词：泉水、春天、弹跳。
B这个句子的字面意思是：如果你终于得到这样的背包，过马路时一定要两面都看看。也就是说，不要因为同时玩着游戏，听着音乐、看着电视，太专注以致不注意来往车辆了