Petroleum, consisting ofcrudeoil and natural gas, seems tooriginatefromorganicmatter inmarinesediment. Microscopic organismssettleto the seafloor andaccumulateinmarinemud. Theorganicmatter maypartiallydecompose, using up the dissolvedoxygenin thesediment. As soon as theoxygenis gone,decaystops and theremainingorganicmatter is preserved.

Continuedsedimentation—theprocessof deposits’ settling on the sea bottom—buries theorganicmatter and subjects it to higher temperatures and pressures, whichconverttheorganicmatter to oil and gas. Asmuddysediments are pressed together, the gas and small droplets of oil may be squeezed out of the mud and may move into sandy layers nearby. Over long periods of time (millions of years), accumulations of gas and oil cancollectin the sandy layers. Both oil and gas are lessdensethan water, so they generallytendto rise upwardthroughwater-saturated rock andsediment.

Oil pools arevaluableundergroundaccumulations of oil, and oil fields are regions underlain by one or more oil pools. When an oil pool orfieldhas been discovered, wells are drilled into the ground. Permanenttowers, called derricks, used to be built tohandlethe long sections of drillingpipe. Nowportabledrilling machines are set up and are then dismantled and removed. When the well reaches a pool, oil usually rises up the well because of itsdensitydifferencewith waterbeneathit or because of thepressureof expanding gas trapped above it. Although this rise of oil is almost always carefully controlled today, spouts of oil, or gushers, werecommonin the past. Gaspressuregraduallydies out, and oil is pumped from the well. Water or steam may be pumped downadjacentwells to help push the oil out. At a refinery, thecrudeoil fromundergroundis separated into natural gas,gasoline,kerosene, and various oils. Petrochemicals such as dyes,fertilizer, andplasticare also manufactured from thepetroleum.

As oil becomes increasingly difficult to find, the search for it is extended into more-hostile environments. Thedevelopmentof the oilfieldon the North Slope of Alaska and theconstructionof the Alaska pipeline are examples of the great expense and difficulty involved in new oil discoveries. Offshore drilling platformsextendthe search for oil to the ocean’scontinentalshelves—those gently slopingsubmarineregions at the edges of the continents. More than one-quarter of the world’s oil and almost one-fifth of the world’s natural gas come from offshore,eventhough offshore drilling is six to seven times more expensive than drilling on land. Asignificantpart of this oil and gas comes from under the North Sea between Great Britain and Norway.

Ofcourse, there is far more oilundergroundthan can be recovered. It may be in a pool too small or too far from apotentialmarkettojustifythe expense of drilling. Some oil lies under regions where drilling is forbidden, such as national parks or other public lands. Evengiventhe best extraction techniques, only about 30 to 40 percent of the oil in agivenpool can be brought to the surface. The rest is far too difficult toextractand has toremainunderground.

Moreover, gettingpetroleumout of the ground and from under the sea and to the consumer can createenvironmentalproblems anywherealongtheline. Pipelines carrying oil can be broken by faults or landslides, causing serious oil spills. Spillage from huge oil-carryingcargoships, called tankers, involved in collisions or accidental groundings (such as the one off Alaska in 1989) can create oil slicks at sea. Offshore platforms may also lose oil, creating oil slicks thatdriftashore andfoulthe beaches, harming the environment. Sometimes, the ground at an oilfieldmay subside as oil is removed. The Wilmingtonfieldnear LongBeach, California, has subsided nine meters in 50 years; protective barriers have had to be built to prevent seawater from flooding the area. Finally, the refining and burning ofpetroleumand its products can causeairpollution. Advancing technology andstrictlaws, however, are helping control some of theseadverseenvironmentaleffects.

Questions:
question_stem: The word “accumulate” in the passage is closest in meaning to
choices: tag: A
text: grow up

tag: B
text: build up

tag: C
text: spread out

tag: D
text: break apart
answer_key: B
explanation: B accumulate: 沉积，聚集，累积之意。A 是成长；B 是增进，积累；C 是展开，铺开；D 是使…分裂。所以 B 的 build up 正确。

question_stem: According to paragraph 1, which of the following is true about petroleum formation?
choices: tag: A
text: Microscopic organisms that live in mud produce crude oil and natural gas.

tag: B
text: Large amounts of oxygen are needed for petroleum formation to begin.

tag: C
text: Petroleum is produced when organic material in sediments combines with decaying marine organisms.

tag: D
text: Petroleum formation appears to begin in marine sediments where organic matter is present.
answer_key: D
explanation: D 以 petroleum formation 做关键词，没有，但有 petroleum originate from blablabla，说石油起源于海洋沉积物当中的有机物，与 D 选项说的完全一致，D 正确；A 错，原文没说 live；B 错，原文没说需要大量氧气，只说用光了氧气之后有机物能够保存；C 错，原文没说 combine。

question_stem: In paragraphs 1 and 2, the author’s primary purpose is to
choices: tag: A
text: describe how petroleum is formed

tag: B
text: explain why petroleum formation is a slow process

tag: C
text: provide evidence that a marine environment is necessary for petroleum formation

tag: D
text: show that oil commonly occurs in association with gas
answer_key: A
explanation: A, 问两段，分别看两段的开头，第一段开头说石油是怎么开始的，第二段第一句说继续沉积 blabla，也就是在延续第一段所说的石油的形成过程，所以 A 正确。

question_stem: Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
choices: tag: A
text: Higher temperatures and pressures promote sedimentation, which is responsible for petroleum formation.

tag: B
text: Deposits of sediments on top of organic matter increase the temperature of and pressure on the matter.

tag: C
text: Increase pressure and heat from the weight of the sediment turn the organic remains into petroleum.

tag: D
text: The remains of microscopic organisms transform into petroleum once they are buried under mud.
answer_key: C
explanation: C 去掉原句中的插入语，原句变成了 sedimentation bury and subject to blabla，convert to petro。A 错，原文没说温度压力提升 sedimentation；B 遗漏了重要信息，原句的变成石油没说；C 正确；D 完全没重现原文的重要信息，错。

question_stem: The word “adjacent” in the passage is closest in meaning to
choices: tag: A
text: nearby

tag: B
text: existing

tag: C
text: special

tag: D
text: deep
answer_key: A
explanation: A adjacent 相邻的，临近的，答案 A，原句说水或者蒸汽可以从什么样的井弄下去，把油压出来。根据物理学的 U 型管原理，从注水的 U 型管一端向管内吹起，另外一端的液面就会上升，同理，从临近的油井压入水或者蒸汽，石油就会被压出来，所以答案是 A，B 存在 C 特殊 D 深都不对。

question_stem: Which of the following can be inferred from paragraph 3 about gushers?
choices: tag: A
text: They make bringing the oil to the surface easier.

tag: B
text: They signal the presence of huge oil reserves.

tag: C
text: They waste more oil than they collect.

tag: D
text: They are unlikely to occur nowadays.
answer_key: D
explanation: 以 gusher 做关键词定位至本段倒数第五句：Although this rise of oil is almost always carefully controlled today, spouts of oil, or gushers, were common in the past. 说 gusher 在过去是非常普遍的，意思就是现在不普遍了，而且前半句还说仔细控制了，仔细控制的结果就是不再发生了，也能选出 D 答案。

question_stem: Which of the following strategies for oil exploration is described in paragraph 4?
choices: tag: A
text: Drilling under the ocean’s surface

tag: B
text: Limiting drilling to accessible locations

tag: C
text: Using highly sophisticated drilling equipment

tag: D
text: Constructing technologically advanced drilling platforms
answer_key: A
explanation: A 第四段第一句就说了 hostile environment，紧接着就用大量文字写了“海上钻井平台”，第五段第一句话也说了在 underground 的地方有更多的油，所以 A 的 under the ocean’s surface 最靠谱；B 明显和第四段第一句说反了；C 的 equipment 和 D 的 advanced platform 都没说。

question_stem: What does the development of the Alaskan oil field mentioned in paragraph 4 demonstrate?
choices: tag: A
text: More oil is extracted from the sea than from land.

tag: B
text: Drilling for oil requires major financial investments.

tag: C
text: The global demand for oil has increased over the years.

tag: D
text: The North Slope of Alaska has substantial amounts of oil.
answer_key: B
explanation: B 第二句和第三句说到了阿拉斯加的石油开采是一个例子，great expense and difficulty involved in new oil discoveries，说明使用开采花钱又需要技术，正确答案 B，需要大量投资；其他选项都没说。

question_stem: The word “sloping” in the passage is closest in meaning to
choices: tag: A
text: shifting

tag: B
text: inclining

tag: C
text: forming

tag: D
text: rolling
answer_key: B
explanation: B slope: 坡，sloping: 倾斜的，斜坡的。A 是移动的；B 是倾斜的；C 是形成；D 是旋转的。根据词意，B 是正确的。

question_stem: According to paragraph 5, the decision to drill for oil depends on all of the following factors EXCEPT
choices: tag: A
text: permission to access the area where oil has been found

tag: B
text: the availability of sufficient quantities of oil in a pool

tag: C
text: the location of the market in relation to the drilling site

tag: D
text: the political situation in the region where drilling would occur
answer_key: D
explanation: D 排除法，A 对应第三句，因为有 drilling is forbidden，正确，不选；B 对应倒数第二句，pool，正确，不选；C 项对应第二句，location of the market，正确，不选；D 没说，错，选。

question_stem: The word “foul” in the passage is closest in meaning to
choices: tag: A
text: reach

tag: B
text: flood

tag: C
text: pollute

tag: D
text: alter
answer_key: C
explanation: C foul 弄脏，污染，污秽的，所以 pollute 正确。原句说海上钻井平台有可能漏油，产生海面浮油，并且怎么样海滩，之前都说了一大堆不好的事儿，所以 pollute 正确，A 到达 B 冲刷 D 改变感情色彩都不对。

question_stem: In paragraph 6, the author’s primary purpose is to
choices: tag: A
text: provide examples of how oil exploration can endanger the environment

tag: B
text: describe accidents that have occurred when oil activities were in progress

tag: C
text: give an analysis of the effects of oil spills on the environment

tag: D
text: explain how technology and legislation help reduce oil spills
answer_key: A
explanation: A，问整个第六段，看第一句，说整个从石油开采一直到市场上的任何一环都有可能污染环境，所以 A 是正确答案；只是说有可能污染环境，没说事故，B 不对；原文只是给出事实，没有任何分析，C 错；D 错因为没说减少污染。