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Plant Gas Previously，researchers had thought that it was impossible for plants to make significant amounts of the gas.They had assumed that，microbes2 need to be in environments without oxygen to produce methane.Methane is a greenhouse gas，like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earths atmosphere and contributeto global warming. With the dried plants，the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C，they found，a gram of dried plant material released up to 3 nanograms of methane per hour. With every 10-degree rise in temperature，the amount of methane released each hour roughly doubled. Beeause there was plenty of oxygen available，its unlikely that the types of bacteria that normally make methane were involved. Experiments on plants that weregrown in water rather than soil also resulted in methane emissions.Thats another strong sign that the gas came from the plants and not soil microbes. 注释： microbe：细菌，意义同bacterium。但microbe不用作专门术语。 练习： A h was produced from plants． C It was produced in oxygen-free environments． To test whether plants are a sot，roe of methane，the scientists created B an environment with the same concentration of oxygen as the Earth has． D an environment filled with the greenhouse gas． A The lower the temperature，the higher the amount of methane emissions． C When exposed to sunlight，plants stop releasing methane． Which of the following about methane is Not mentioned in the passage? B Plants growing in water release methane． D Microbes in plants produce methane． A Methane becomes less poisonous． C Less methane reaches the atmosphere． 答案与题解： 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．．．。 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。 C 最后一段的第二句可以找到本题的答案。 | 
