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  3. Renewable energy sources can be replenished in a short period of time. The five renewable sources used most often include hydrop

Renewable energy sources can be replenished in a short period of time. The five renewable sources used most often include hydrop

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问题      Renewable energy sources can be replenished in a short period of time. The five renewable sources used most often include hydropower (water), solar, wind, geothermal, and biomass. Renewable energy’s impact on the world’s energy picture is significant. Many important events have occurred during the history of using renewable sources to generate electricity--but the overall consumption from renewable energy sources has declined by about 15 percent from their I996 peak to about 6 quads in 2005.
     The use of renewable energy is not new. Five generations (125 years) ago, wood supplied up to 90 percent of our energy needs. Due to the convenience and low prices of fossil fuels, wood use has fallen. Now, the biomass which would normally present a disposal problem is converted into electricity (e.g., manufacturing wastes, rice hulls, and black liquor from paper production).
     Historically, low fossil fuel prices, especially for natural gas, have made growth difficult for renewable fuels.  The deregulation and restructuring of the electric power industry could have a major impact on renewable energy consumption. Demands for cheaper power in the short term would likely decrease demand for renewable energy, while preferences for renewables included in some versions of proposed electricity restructuring legislation would breathe new life into this industry.
     Use of renewables in the United States is not currently expected to approach that of the major fuels, and due to their limitatious (e.g., their intermittent nature-cloudy days have no solar gain, quiet days mean no wind blows to drive wind turbines, dams are primarily for flood control, so hydroelectricity production varies as dams’ water levels change), renewables may never provide "the" answer to all energy problems. Around the world, renewable energy is proving to be of great value.
     In 2005, about 6.1 Quadrillion Btu (Quads) of U.S. energy came from renewable fuels. Each of the energy sources we use is measured, purchased, and sold in a different form. Many units of measurement are used to measure the energy we use each day.  
Why did wood use fall several generations ago?
选项 A、Because wood occupied 90 % of mankind’s energy needs.
B、Wood supply was insufficient.
C、Fossil fuels have some advantages.
D、Bionass presented a disposal problem.
答案C
解析 细节理解题。对应文中第二段Due to the convenience and low prices of fossil fuels，wood use has fallen．因此C正确。
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