A.over the past 50 years B.beneath the earth’s surface C.by more than 50 percent D.for more than four decades E.as a raw mat

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问题 A.over the past 50 years
B.beneath the earth’s surface
C.by more than 50 percent
D.for more than four decades
E.as a raw material
F.for home energy needs  
Natural gas is recognized as the most economical energy source______.

选项

答案F

解析 文章第二段第四句指出,实际上,天然气是家庭能源需求中最经济的能源,是电能的三分之一。F项for home energy needs(家庭能源需求)与原句意思相符,故选F。
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