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OFFICIAL43 All of the following are cited in paragraph 2 as evidence that petroleum is a product of the decomposition of organic matter EXCEPT

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The Origin Of Petroleum
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Petroleum is defined as a gaseous, liquid, and semisolid naturally occurring substance that consists chiefly of hydrocarbons (chemical compounds of carbon and hydrogen). Petroleum is therefore a term that includes both oil and natural gas. Petroleum is nearly always found in marine sedimentary rocks. In the ocean, microscopic phytoplankton (tiny floating plants) and bacteria (simple, single-celled organisms) are the principal sources of organic matter that is trapped and buried in sediment. Most of the organic matter is buried in clay that is slowly converted to a fine-grained sedimentary rock known as shale. During this conversion, organic compounds are transformed to oil and natural gas.

Sampling on the continental shelves and along the base of the continental slopes has shown that fine muds beneath the seafloor contain up to 8 percent organic matter. Two additional kinds of evidence support the hypothesis that petroleum is a product of the decomposition of organic matter: oil possesses optical properties known only in hydrocarbons derived from organic matter, and oil contains nitrogen and certain compounds believed to originate only in living matter. A complex sequence of chemical reactions is involved in converting the original solid organic matter to oil and gas, and additional chemical changes may occur in the oil and gas even after they have formed.

It is now well established that petroleum migrates through aquifers and can become trapped in reservoirs. Petroleum migration is analogous to groundwater migration. When oil and gas are squeezed out of the shale in which they originated and enter a body of sandstone or limestone somewhere above, they migrate readily because sandstones (consisting of quartz grains) and limestones (consisting of carbonate minerals) are much more permeable than any shale. The force of molecular attraction between oil and quartz or carbonate minerals is weaker than that between water and quartz or carbonate minerals. Hence, because oil and water do not mix, water remains fastened to the quartz or carbonate grains, while oil occupies the central parts of the larger openings in the porous sandstone or limestone. Because oil is lighter than water, it tends to glide upward past the carbonate- and quartz-held water. In this way, oil becomes segregated from the water; when it encounters a trap, it can form a pool.

Most of the petroleum that forms in sediments does not find a suitable trap and eventually makes its way, along with groundwater, to the surface of the sea. It is estimated that no more than 0.1 percent of all the organic matter originally buried in a sediment is eventually trapped in an oil pool. It is not surprising, therefore, that the highest ratio of oil and gas pools to volume of sediment is found in rock no older than 2.5 million years - young enough so that little of the petroleum has leaked away - and that nearly 60 percent of all oil and gas discovered so far has been found in strata that formed in the last 65 million years This does not mean that older rocks produced less petroleum; it simply means that oil in older rocks has had a longer time in which to leak away.

How much oil is there in the world? This is an extremely controversial question. Many billions of barrels of oil have already been pumped out of the ground. A lot of additional oil has been located by drilling but is still waiting to be pumped out. Possibly a great deal more oil remains to be found by drilling. Unlike coal, the volume of which can be accurately estimated, the volume of undiscovered oil can only be guessed at. Guesses involve the use of accumulated experience from a century of drilling. Knowing how much oil has been found in an intensively drilled area, such as eastern Texas, experts make estimates of probable volumes in other regions where rock types and structures are similar to those in eastern Texas. Using this approach and considering all the sedimentary basins of the world, experts estimate that somewhere between 1,500 and 3,000 billion barrels of oil will eventually be discovered.

3.All of the following are cited in paragraph 2 as evidence that petroleum is a product of the decomposition of organic matter EXCEPT

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正确答案:B
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【题目翻译】以下所有内容在第2段中均被引用为石油是有机物分解产物的证据,除非 A:在海底以下的泥层中发现的有机物量。 B:石油和天然气形成后发生的化学变化。 C:油的光学性质 D:石油中含有氮和其他有机化合物的事实 【判定题型】:根据题干中出现的大写“EXCEPT”/"NOT" 等其他明显表示否定的词,可以判定本题为否定事实信息题,需要找出与原文信息不符的那个答案。 【关键词定位】:根据题干关键词“the decomposition of organic matter”,可以将出题范围锁定在Passage2 。 【选项分析】 A:选项对应文章第一句话,提到海底泥浆中含有高达8%的有机物,故A选项符合原文,排除。 B:选项在最后一句有提到,但是无关缠绕信息,所以B为正确答案。 C:第二句话说“two additional kinds of evidence”对应了C选项。排除。 D:原文optical properties of oil 对应D选项:石油所含的氮和某些化合物,来源于有机物。故排除。

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