練習：
1． What was scientists understanding of methane?
A h was produced from plants．
B It was not a greenhouse gas．
C It was produced in oxygen-free environments．
D It traps more heat than any other greenhouse gas．
2． To test whether plants are a sot，roe of methane，the scientists created
A a oxygen-free environment．
B an environment with the same concentration of oxygen as the Earth has．
C a carbon dioxide-free environment．
D an environment filled with the greenhouse gas．
3． Which statement is true of the methane emissions of plants in the experiment?
A The lower the temperature，the higher the amount of methane emissions．
B I．iving plants release less methane than dried plants at the same temperature．
C When exposed to sunlight，plants stop releasing methane．
D The higher the temperature，the greater the amount of methane emissions．
4． Which of the following about methane is Not mentioned in the passage?
A Plants growing in soil release methane．
B Plants growing in water release methane．
C Soil microbes consume methane．
D Microbes in plants produce methane．
5． What is the beneficial point of some microbes consuming plant-produced methane?
A Methane becomes less poisonous．
B Methane is turned into a fertilizer．
C Less methane reaches the atmosphere．
D Air becomes cleaner．
答案與題解：
1． C 短文的第一和第二段都講到，科學家過去曾經(jīng)認為，沼氣必須在無氧的環(huán)境中才能產(chǎn)生。注意，作者用的是過去式：Most scientists assumed that．．．They had assumed that．．．。
2． B 第三段第一句說，科學家使用密封的房間來做實驗，房間里氧氣的濃度與地球大氣中的氧氣濃度相仿。所以B句符合原文的意思，其他三個選擇則不符合原文內(nèi)容。
3． D 根據(jù)第四和第五段的內(nèi)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。
4． D 最后兩段告訴我們，無論在土壤中還是在水中生長的植物都能釋放沼氣，土壤中的微生物消耗沼氣，使沼氣不至于進入空氣。所以A、B、C的內(nèi)容均符合短文最后兩段中作者的意思。D的內(nèi)容短文中沒有提到。
5． C 最后一段的第二句可以找到本題的答案。
1． What was scientists understanding of methane?
A h was produced from plants．
B It was not a greenhouse gas．
C It was produced in oxygen-free environments．
D It traps more heat than any other greenhouse gas．
2． To test whether plants are a sot，roe of methane，the scientists created
A a oxygen-free environment．
B an environment with the same concentration of oxygen as the Earth has．
C a carbon dioxide-free environment．
D an environment filled with the greenhouse gas．
3． Which statement is true of the methane emissions of plants in the experiment?
A The lower the temperature，the higher the amount of methane emissions．
B I．iving plants release less methane than dried plants at the same temperature．
C When exposed to sunlight，plants stop releasing methane．
D The higher the temperature，the greater the amount of methane emissions．
4． Which of the following about methane is Not mentioned in the passage?
A Plants growing in soil release methane．
B Plants growing in water release methane．
C Soil microbes consume methane．
D Microbes in plants produce methane．
5． What is the beneficial point of some microbes consuming plant-produced methane?
A Methane becomes less poisonous．
B Methane is turned into a fertilizer．
C Less methane reaches the atmosphere．
D Air becomes cleaner．
答案與題解：
1． C 短文的第一和第二段都講到，科學家過去曾經(jīng)認為，沼氣必須在無氧的環(huán)境中才能產(chǎn)生。注意，作者用的是過去式：Most scientists assumed that．．．They had assumed that．．．。
2． B 第三段第一句說，科學家使用密封的房間來做實驗，房間里氧氣的濃度與地球大氣中的氧氣濃度相仿。所以B句符合原文的意思，其他三個選擇則不符合原文內(nèi)容。
3． D 根據(jù)第四和第五段的內(nèi)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。
4． D 最后兩段告訴我們，無論在土壤中還是在水中生長的植物都能釋放沼氣，土壤中的微生物消耗沼氣，使沼氣不至于進入空氣。所以A、B、C的內(nèi)容均符合短文最后兩段中作者的意思。D的內(nèi)容短文中沒有提到。
5． C 最后一段的第二句可以找到本題的答案。