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阅读下面的短文。每篇短文的后面有五个问题，每个问题有四个备选答案。请根据短文的内容选择最佳答案。每个试题计3分,共计15分。
Scientists have been studying natural sources of methane for decades but hadnt regarded plants as a producer，notes Frank Keppler，a geochem[st at the Max Planck Institute for Nuclear Physics in Heidelberg，Germany1.Now Keppler and his colleagues find that plants，from grasses to trees，may also be sources of the greenhouse gas.This is really surprising，because most scientists assumed that methane production requires an oxygen-free environment.
In its experiments，Kepplers team used sealed chambers that contained the same concentration of oxygen that Earths atmosphere has.They measured the amounts of methane that were released by both living plants;and dried plant material，such as fallen leaves.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour.Methane emissions tripled when living and dead plant was exposed to sunlight.
The new finding is an interesting observation, says Jennifer Y.King，a biogeochemist at the University of Minnesota in St.Paul3.Because some types of soil microbes consume methane，they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plants influence，she notes.
methanen.甲烷，沼气 emissionn.散发，发射
Celsius n..adj.摄氏(的) bacterian.细菌
biogeochemist n.生物地球化学家 chambern.室，房间;腔
1. the Max Planck Institute for Nuclear Physics in Heidelberg，Germany：马克思普朗克核物理研究所，位于德国海德堡。海德堡系德国西南部城市，在巴登一符腾堡州的内卡河畔。海德堡大学是德国历史最悠久的大学。
3. St.Paul：圣保罗，美国明尼苏达州首府。
1. What was scientists understanding of methane?
B It was not a greenhouse gas.
D It traps more heat than any other greenhouse gas.
A a oxygen-free environment.
C a carbon dioxide-free environment.
3. Which statement is true of the methane emissions of plants in the experiment?
B I.iving plants release less methane than dried plants at the same temperature.
D The higher the temperature，the greater the amount of methane emissions.
A Plants growing in soil release methane.
C Soil microbes consume methane.
5. What is the beneficial point of some microbes consuming plant-produced methane?
B Methane is turned into a fertilizer.
D Air becomes cleaner.
1. C 短文的第一和第二段都讲到，科学家过去曾经认为，沼气必须在无氧的环境中才能产生。注意，作者用的是过去式：Most scientists assumed that...They had assumed that...。
3. D 根据第四和第五段的内容，只有D是正确的说法。温度越高沼气的释放量越高，有生命的植物释放的沼气远大于干植物的释放量，在阳光下，它们的沼气释放量是正常情况的三倍。
5. C 最后一段的第二句可以找到本题的答案。
阅读下面的短文。每篇短文的后面有五个问题，每个问题有四个备选答案。请根据短文的内容选择最佳答案。每个试题计3分,共计15分。
Scientists have been studying natural sources of methane for decades but hadnt regarded plants as a producer，notes Frank Keppler，a geochem[st at the Max Planck Institute for Nuclear Physics in Heidelberg，Germany1.Now Keppler and his colleagues find that plants，from grasses to trees，may also be sources of the greenhouse gas.This is really surprising，because most scientists assumed that methane production requires an oxygen-free environment.
In its experiments，Kepplers team used sealed chambers that contained the same concentration of oxygen that Earths atmosphere has.They measured the amounts of methane that were released by both living plants;and dried plant material，such as fallen leaves.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour.Methane emissions tripled when living and dead plant was exposed to sunlight.
The new finding is an interesting observation, says Jennifer Y.King，a biogeochemist at the University of Minnesota in St.Paul3.Because some types of soil microbes consume methane，they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plants influence，she notes.
methanen.甲烷，沼气 emissionn.散发，发射
Celsius n..adj.摄氏(的) bacterian.细菌
biogeochemist n.生物地球化学家 chambern.室，房间;腔
1. the Max Planck Institute for Nuclear Physics in Heidelberg，Germany：马克思普朗克核物理研究所，位于德国海德堡。海德堡系德国西南部城市，在巴登一符腾堡州的内卡河畔。海德堡大学是德国历史最悠久的大学。
3. St.Paul：圣保罗，美国明尼苏达州首府。
1. What was scientists understanding of methane?
B It was not a greenhouse gas.
D It traps more heat than any other greenhouse gas.
A a oxygen-free environment.
C a carbon dioxide-free environment.
3. Which statement is true of the methane emissions of plants in the experiment?
B I.iving plants release less methane than dried plants at the same temperature.
D The higher the temperature，the greater the amount of methane emissions.
A Plants growing in soil release methane.
C Soil microbes consume methane.
5. What is the beneficial point of some microbes consuming plant-produced methane?
B Methane is turned into a fertilizer.
D Air becomes cleaner.
1. C 短文的第一和第二段都讲到，科学家过去曾经认为，沼气必须在无氧的环境中才能产生。注意，作者用的是过去式：Most scientists assumed that...They had assumed that...。
3. D 根据第四和第五段的内容，只有D是正确的说法。温度越高沼气的释放量越高，有生命的植物释放的沼气远大于干植物的释放量，在阳光下，它们的沼气释放量是正常情况的三倍。
5. C 最后一段的第二句可以找到本题的答案。
