閱讀下面的短文。每篇短文的后面有五個問題，每個問題有四個備選答案。請根據短文的內容選擇最佳答案。每個試題計3分,共計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，沼氣 emissionn.散發，發射

　　Celsius n..adj.攝氏(的) bacterian.細菌

　　biogeochemist n.生物地球化學家 chambern.室，房間;腔

　　1. the Max Planck Institute for Nuclear Physics in Heidelberg，Germany：馬克思普朗克核物理研究所，位于德國海德堡。海德堡系德國西南部城市，在巴登一符騰堡州的內卡河畔。海德堡大學是德國歷史最悠久的大學。

　　3. St.Paul：圣保羅，美國明尼蘇達州首府。

　　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講到，科學家過去曾經認為，沼氣必須在無氧的環境中才能產生。注意，作者用的是過去式：Most scientists assumed that...They had assumed that...。

　　3. D 根據第四和第五段的內容，只有D是正確的說法。溫度越高沼氣的釋放量越高，有生命的植物釋放的沼氣遠大于干植物的釋放量，在陽光下，它們的沼氣釋放量是正常情況的三倍。

　　5. C 最后一段的第二句可以找到本題的答案。

　　閱讀下面的短文。每篇短文的后面有五個問題，每個問題有四個備選答案。請根據短文的內容選擇最佳答案。每個試題計3分,共計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，沼氣 emissionn.散發，發射

　　Celsius n..adj.攝氏(的) bacterian.細菌

　　biogeochemist n.生物地球化學家 chambern.室，房間;腔

　　1. the Max Planck Institute for Nuclear Physics in Heidelberg，Germany：馬克思普朗克核物理研究所，位于德國海德堡。海德堡系德國西南部城市，在巴登一符騰堡州的內卡河畔。海德堡大學是德國歷史最悠久的大學。

　　3. St.Paul：圣保羅，美國明尼蘇達州首府。

　　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講到，科學家過去曾經認為，沼氣必須在無氧的環境中才能產生。注意，作者用的是過去式：Most scientists assumed that...They had assumed that...。

　　3. D 根據第四和第五段的內容，只有D是正確的說法。溫度越高沼氣的釋放量越高，有生命的植物釋放的沼氣遠大于干植物的釋放量，在陽光下，它們的沼氣釋放量是正常情況的三倍。

　　5. C 最后一段的第二句可以找到本題的答案。