|
Backpacks are convenient. They can hold your books，your lunch，and achange of clothes，leaving your hands free to do other things.Someday，if youdont mind carrying a heavy load，your backpacks might also power your MP31player，keep your cell phone running，and maybe even light your wayhome. The backpacks electricity-creating powers depend onsprings used to hang a cloth pack from its metal frame.The frame sits againstthe wearers back，and the whole pack moves up and down as the person walks.Agear mechanism converts vertical movements of the pack to rotary motions of anelectrical generator，producing up to 7.4 watts. The backpack could be especially useful forsoldiers，scientists，mountaineers，and emergency workers who typically carryheavy backpacks.For the rest of us，power-generating backpacks could make itpossible to walk，play video games，watch TV，and listen to music，all at the sametime.Electricity-generating packs arent on the market yet，but if you do get one eventually，just make sure to look both ways before crossing thestreet! 1. Backpacks are convenient because B they can hold as many things as you want to carry. D you do not have to carry things withyou. and his colleagues? B It can be used as cellphones，GPS in the military actions or field studies. D It is light and easy to carry. A a small stream of water flowing naturally from theearth. C the act or an instance of jumping or leaping. being pushed. A To make the backpackmore comfortable for the wearer. C To test the advantage of the backpack. 5. What is implied in if you do get oneeventually，just make sure to took both A You will be too excited to watch the traffic. C It is notpossible for you to get such a backpack. 答案与题解： 2.A第二段的第一句说，Lawrence C.Rome及其同事们发明的这种背包，当背着背包走路时，会有电能产生;该段最后一句告诉我们，背包的这种性能可减少背包的重量，因为不必携带备用电池。 4.B 第四段最后一句的意思是：Rome计划将这种背包商业化，即推向市场。A、C、D在文中均未提到。D的意思是为背包做广告。 | 
