sources in the city stream into space and illuminate the night sky.
C The night sky is illuminated by the lights from big glowing cities in the night.
D Stargazing becomes difficult because there is a layer of haze in the air.
38. Does the writer think growing cities affect astronomers' work? Why does he think so?
A Yes. Because the once dark rural areas are polluted by lights.
B No. Because they can still see stars in rural areas.
C Yes. Because rural areas are not a good place for astronomers to study stars.
D No. Because faint light given off by stars can still be seen on a clear night.
39. How does light pollution affect wildlife.9 Which of the following is NOT correct?
A Animals may go off course due to the attraction of artificial lights.
B Animals might be attracted by artificial lights to go into cities.
C Artificial lights at night may make migrating birds lose their way.
D Attracted by artificial lights, birds fly into lighted buildings.
40. Which of the following is closest in meaning to the title "Light Night, Dark Stars" ?
A The night sky is light colored and stars are black.
B Lights appear at night and stars are seen in the dark.
C City lights illuminate the night sky and make stars invisible.
D City lights at night illuminate stars in the sky.
第三篇 Electric Backpack
Backpacks are convenient. They can hold your books, your lunch, and a change of clothes, leaving your hands free to do other things. Someday, if you don't mind carrying a heavy load, your backpacks might also power your MP31 player, keep your cell phone running, and maybe even light your way home.
Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia2 and the Marine Biological Laboratory in Woods Hole3, Mass. 4, have invented a backpack that makes electricity from energy produced while its wearer walks. In military actions, search-and-rescue operations, and scientific field studies, people rely increasingly on cell phones, global positioning system (GPS)5 receivers, night-vision goggles, and other battery-powered devices to get around and do their work. The backpack's electricity-generating feature could dramatically reduce the amount of a wearer's load now devoted to spare batteries, report Rome and his colleagues in the Sept. 9
Science6.
The backpack's electricity-crew, ring powers depend on springs used to hang a cloth pack from its metal frame. The frame sits against the wearer’s back, and the whole pack moves up and down as the person walks. A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator, producing up to 7.4 watts.
Unexpectedly, tests showed that wearers of the new backpack alter their gaits in response to the pack's oscillations, so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage, Rome plans to commercialize both electric and non-electric versions of the backpack.
The backpack could be especially useful for soldiers, scientists, mountaineers, and emergency workers who typically carry heavy backpacks. For the rest of us, power-generating backpacks could make it possible to walk, play video games, watch TV, and listen to music, all at the same time. Electricity-generating packs aren't on the market yet, but if you do get one eventually, just make sure to look Both ways before crossing the street! <
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