[单项选择]The night is not what it was. Once, the earth was cast half in shadow. Then came fire, candle, and light bulb, gradually drawing back the curtain of darkness. But a brighter world has its drawbacks. An estimated 30 percent of outdoor lighting—plus even some indoor lighting—is wasted. Inefficient lighting costs U.S. about $10.4 billion a year, according to bob Gent of the International Dark Sky Association, a nonprofit that aims to control light pollution.
Last year, in Sydney, an estimated 2.2 million Australians switched off their lights during "Earth Hour", briefly reducing that city’s energy use by more than 10 percent. Motivated by such trends, more than two dozen cities worldwide went dim on March 29 this year in an hour-long demonstration.
A number of groups are trying to measure light pollution and assess its effect on the environment in the hope that people will reduce their own contribution to the problem. Scientists are trying to report how many stars we
A. lose the chance to gaze stars
B. have a higher risk of health problem
C. have less exposure to white light
D. are able to blame for light pollution

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[单项选择]The night is not what it was. Once, the earth was cast half in shadow. Then came fire, candle, and light bulb, gradually drawing back the curtain of darkness. But a brighter world has its drawbacks. An estimated 30 percent of outdoor lighting—plus even some indoor lighting—is wasted. Inefficient lighting costs U.S. about $10.4 billion a year, according to bob Gent of the International Dark Sky Association, a nonprofit that aims to control light pollution.
Last year, in Sydney, an estimated 2.2 million Australians switched off their lights during "Earth Hour", briefly reducing that city’s energy use by more than 10 percent. Motivated by such trends, more than two dozen cities worldwide went dim on March 29 this year in an hour-long demonstration.
A number of groups are trying to measure light pollution and assess its effect on the environment in the hope that people will reduce their own contribution to the problem. Scientists are trying to report how many stars we can
A. benefits
B. interests
C. effects
D. problems

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[单项选择] Earthquakes What causes earthquakes The earth is formed of layers. The surface of the earth, about 100 kilometers thick, is made of large pieces. When they move against each other, an earth quake happens, A large movement causes a violent earthquake, but a small movement causes a mild one. Earthquakes last only a few seconds. The rolling movements are called seismic (地震的) waves. The seismic waves start in one place, called the epicenter (震中) , and roll outward. A seismic wave travels around the earth in about twenty minutes. Usually, an earthquake is strong enough to cause damage only near its epicenter. However, epicenters at the bottom of the ocean create huge sea waves as tall as 15 meters. These waves cross the ocean in several hours. Rushing toward land, they destroy small islands and ships in their path. When they hit land, they flood coastal areas far from the epicenter of the earthquake. In 1868, a wave reached 4. 5 kilometers inland in P
A. Y
B. N
C. NG

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