Earth'sinternalheat, fueled by radioactivity, provides the energy forplatetectonicsandcontinentaldrift, mountain building, and earthquakes. It can also be harnessed todriveelectric generators and heat homes. Geothermalenergy becomesavailablein apracticalform whenundergroundheat is transferred by water that is heated as it passesthroughasubsurfaceregionof hot rocks (a heatreservoir) that may be hundreds or thousands of feet deep. The water is usually naturally occurringgroundwaterthat seeps downalongfractures in the rock; less typically, the water is artificially introduced by being pumped down from the surface. The water is brought to the surface, as aliquidor steam,throughholes drilled for the purpose.

By far the mostabundantform ofgeothermalenergy occurs at therelativelylow temperatures of 80° to 180°centigrade. Water circulatedthroughheat reservoirs in thistemperaturerange is able toextractenough heat to warmresidential,commercial, andindustrialspaces. More than 20,000 apartments in France are now heated by warmundergroundwater drawn from a heatreservoirin a geologic structure near Paris called the Paris Basin. Iceland sits on avolcanicstructure known as the Mid-Atlantic Ridge. Reykjavik, the capital of Iceland, isentirelyheated bygeothermalenergy derived fromvolcanicheat.

Geothermalreservoirs with temperatures above 180°centigradeare useful for generatingelectricity. Theyoccurprimarilyin regions of recentvolcanicactivityas hot, dry rock; natural hot water; or natural steam. Thelattertwo sources are limited to those few areas where surface water seeps downthroughundergroundfaults or fractures toreachdeep rocks heated by the recentactivityofmoltenrockmaterial. The world's largestsupplyof natural steam occurs at The Geysers, 120 kilometers north of San Francisco, California. In the 1990s enoughelectricityto meet about half the needs of San Francisco was being generated there. Thisfacilitywas then in its thirddecadeof production and was beginning to show signs ofdecline, perhaps because of overdevelopment. By the late 1990s some 70geothermalelectric-generating plants were in operation in California, Utah, Nevada, and Hawaii, generating enough power tosupplyabout a million people. Eighteen countries nowgenerateelectricityusinggeothermalheat.

Extracting heat from very hot, dry rocks presents a more difficult problem: the rocks must be fractured topermitthecirculationof water, and the water must be provided artificially. The rocks are fractured by water pumped down at very high pressures. Experiments are under way to develop technologies for exploiting thisresource.

Like most other energy sources,geothermalenergy presents someenvironmentalproblems. The surface of the ground can sink if hotgroundwateris withdrawn without being replaced. Inaddition, water heated geothermally cancontainsalts andtoxicmaterials dissolved from the hot rock. These waters present adisposalproblem if they are not returned to the ground from which they were removed.

Thecontributionofgeothermalenergy to the world's energy future is difficult toestimate. Geothermalenergy is in asensenot renewable, because in most cases the heat would be drawn out of areservoirmuch more rapidly than it would be replaced by the very slow geological processes by which heat flowsthroughsolidrock into a heatreservoir. However, in many places (for example, California, Hawaii, the Philippines, Japan, Mexico, the rift valleys of Africa)theresourceis potentially so large that its future willdependon the economics of production. At present, we can makeefficientuse of only naturally occurring hot water or steam deposits. Although thepotentialisenormous, it is likely that in the near futuregeothermalenergy can make importantlocalcontributions only where theresourceis close to the user and the economics arefavorable, as they are in California, New Zealand, and Iceland. Geothermalenergy probably will not make large-scale contributions to the world energybudgetuntil well into the twenty-firstcentury, if ever.

Questions:
question_stem: According to the processes described in paragraph 1, what is the relationship between radioactivity and the steam produced by geothermal heat?
choices: tag: A
text: Geothermally heated steam is produced when water is exposed to radioactivity deep underground.

tag: B
text: When water is introduced into holes drilled thousands of feet in the ground, it becomes radioactive and turns to steam.

tag: C
text: Radioactivity heats Earth's interior rock, which in turn can heat water to the point it becomes steam.

tag: D
text: When a reservoir of steam in subsurface rock is produced by radioactivity, it is said to be geothermally heated.
answer_key: C
explanation: C 细细节题，问 radioactivity 和 steam 的关系，所以找双关键词，分别定位至本段第一句和最后一句，第一句说 radioactivity 提供了地球的内热，最后一句说水变成蒸汽到达地表，水受热才能蒸汽，而这份热量是 geothermal energy 提供的，这就是二者的关系，所以答案是 C。A 的水暴露在 radioactive underground 时候 steam 产生没说；B 水变成 radioactive 没说；D 的 radioactivity 产生蒸汽更不靠谱

question_stem: The word "practical" in the passage is closest in meaning to
choices: tag: A
text: usable

tag: B
text: plentiful

tag: C
text: economical

tag: D
text: familiar
answer_key: A
explanation: A practical: 实用的，可用的。A 是可用的，B 是很多的，C 是经济的，节约的，D 是熟悉的。答案是 A 的 usable。

question_stem: The word "abundant" in the passage is closest in meaning to
choices: tag: A
text: economical

tag: B
text: familiar

tag: C
text: plentiful

tag: D
text: useful
answer_key: C
explanation: C abundant: 大量的，充足的。A 是经济的，节约的；B 是熟悉的; C 是许多的，丰富的；D 是有用的。根据词意，答案是 C 的 plentiful。

question_stem: According to paragraph 2, which of the following is true about heat reservoirs with a temperature in the range of 80° to 180° centigrade?
choices: tag: A
text: They are under international control.

tag: B
text: They are more common than reservoirs that have a higher temperature.

tag: C
text: Few of them produce enough heat to warm large industrial spaces.

tag: D
text: They are used to generate electricity.
answer_key: B
explanation: B 以80到180度做关键词定位至第一句，说最丰富的 geothermal energy 是在80到180度范围内的，所以同义替换是 B 的 more common than higher temperature。A 的 international control 原文没说；C 与本段第二句说反；D 在本段没提，但下一段说高于180度的可以用来发电，所以 D 说反了。

question_stem: According to paragraph 3, what is the connection between underground faults and naturally occurring steam?
choices: tag: A
text: Underground faults enable the heat from molten-rock material to escape upward to regions where it can heat surface water enough to produce steam.

tag: B
text: Underground faults are created by steam that is produced in geothermal reservoirs deep inside Earth.

tag: C
text: Underground faults create spaces in which natural steam is sometimes trapped.

tag: D
text: Underground faults allow surface water to reach deep rocks that are hot enough to turn it into steam.
answer_key: D
explanation: D 又是一个问两者关系的题，找双关键词，定位至第三句，说 natural hot water 和 natural steam 仅存在于那些地点，地表水通过 fault 或者 fracture 渗到地下，碰到被加热的 blabla，答案明显是 D。A 说 fault 使 heat 跑上来，和原文的方向说反了，原文是水跑下去；B 说 steam 创造了 fault 完全不靠谱；C 的 steam 被 trap 原文没说。

question_stem: In paragraph 3, why does the author mention that in the 1990s The Geysers was in its third decade of production?
choices: tag: A
text: To provide the historical context of the geothermal production of electricity in the United States

tag: B
text: To imply that The Geysers was the first geothermal site to be put into production in California

tag: C
text: To help explain the signs of decline shown by The Geysers

tag: D
text: To explain why 70 new geothermal sites were put into electricity production in the late 1990s
answer_key: C
explanation: C 修辞目的题，先读例子所在句，只是细节，按照常规应该往前看，但前一句已经在上题看过，与答案无关，所以往下看，而且看下一句另外一个原因是因为代词 this，下句说 G 经历了30年的运作，已经显示衰败迹象，可能是因为过度开发，所以答案是 C，A 和 B 的内容原文没提；D 本身也是个细节。

question_stem: Which of the following can be inferred from paragraphs 2 and 3 about geothermal reservoirs?
choices: tag: A
text: Volcanic heat is associated only with geothermal reservoirs that have a temperature over 180° centigrade.

tag: B
text: More countries produce power from geothermal reservoirs than use them for heating buildings.

tag: C
text: Most geothermal reservoirs are suitable for producing electricity.

tag: D
text: A higher geothermal reservoir temperature is needed to generate electricity than is needed to heat homes.
answer_key: D
explanation: D 此题用排除法更快，A 与第二段首句说反，错；第二段只是说 geothermal energy 可以用来加热 building，没说 most，B 错；C 和 D 都可以从两段的首句看出来，第二段说最多的是在80到180度，第三段说发电需要180度以上，所以发电比别的温度高，D 对，C 说反。

question_stem: According to paragraph 4, extracting heat from very hot, dry rocks is difficult in part because
choices: tag: A
text: the underground rock must be fractured before heat can be removed from it

tag: B
text: the water above the rock is under very high pressure

tag: C
text: the rock breaks apart when water is pumped into it

tag: D
text: the water circulated through the rock must be much cooler than the rock itself
answer_key: A
explanation: A 整个问题做关键词定位至第一句，说从 hot, dry rock 抽热量是特别难的，必须先 fracture rock，水也要人工引入，所以答案是 A。D 没说，B 和 C 原文确实有说，但没有回答为什么难，也就是那种答非所问选项，所以也不对。

question_stem: The word "exploiting" in the passage is closest in meaning to
choices: tag: A
text: locating

tag: B
text: increasing

tag: C
text: making use of

tag: D
text: estimating the size of
answer_key: C
explanation: C exploit: 开发，利用。A 是定位；B 是增加；C 是利用，使用；D 是估算尺寸。所以 C 的 making use of 正确。

question_stem: How is the problem that the surface may sink related to the problem that water heated geothermally may contain toxic materials?
choices: tag: A
text: Both problems could be solved by returning groundwater that is removed from an underground heat reservoir back to the reservoir after heat is extracted from it.

tag: B
text: The problem of sinking is more difficult to solve than is the problem of toxic materials.

tag: C
text: Land at the surface sinks because the rock beneath the surface is weakened when salts and toxic materials are removed from it in the process of extracting geothermal energy.

tag: D
text: Both problems are caused by the fact that the hot groundwater in a heat reservoir dissolves the rock, which weakens the rock and makes the water toxic with salt.
answer_key: A
explanation: A 又是一个问两者关系的题，本来应该找双关键词，但这段实在太短，找关键词还不如读完。快速扫完之后发现这两件事情都是由于开采地下水引起的问题，第二句话中强调了如果地下水被抽掉之后，如果不补充回去，地表就会下沉；而且最后一句说如果不把地下水补充回去，这些水就会有就会有清理的问题，因为他们含有有毒物质。所以解决两个问题的办法就是将抽出的地下水补充回去，所以答案是 A。两个问题之间是并列关系，既没有比较也没有因果，所以 B 和 C 都不对；D 的 dissolved 溶解原文没说，也不对。

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: Heat flows through solid rock very slowly, so it takes a very long time for geological processes to produce a reservoir of geothermal energy.

tag: B
text: Geothermal energy is not renewable because heat flows very slowly through solid rock into or out of a heat reservoir.

tag: C
text: The heat quickly removed from a heat reservoir is replaced so slowly by geological processes that geothermal energy is not practically speaking, renewable.

tag: D
text: In most cases, heat travels into a heat reservoir so slowfy that it is a much quicker process to remove the heat from a reservoir than to replace it.
answer_key: C
explanation: C 原句的主要逻辑是因果，结果是 geothermal energy 是不 renewable 的，原因是抽取的速度远远快于补给的速度，而因果逻辑中，结果尤其重要，所以前面的结果一定要有，A 和 D 排除；原句中的另一个逻辑关系出现在原因中，原因中有一个比较，说 draw out 比 replace 的快，C 重现了这个比较，B 没有，所以正确答案是 C。

question_stem: In paragraph 6, the author implies that in California, Hawaii, the Philippines, Japan, Mexico, and the rift valleys of Africa the potential size of the geothermal resource is so large that
choices: tag: A
text: it might be economically worth developing these sites even though geothermal energy is not renewable

tag: B
text: these sites will be the first geothermal energy sites to be developed with new technology

tag: C
text: these sites are likely to make a large-scale contribution to the world energy budget in the twenty-first century

tag: D
text: it does not matter whether they have naturally occurring deposits of hot water or steam
answer_key: A
explanation: A 先读细节所在句，说在这些资源如此充足的地方，资源的利用前景取决于 economies of production 生产经济，四个答案中只有 A 提到了开采是否划算的问题，所以答案是 A。B 和 D 原文直接没说；C 跑到最后一句去了，跟例子也没什么关系，注意倒数第二句 MS 也有例子，但是题目问的不是那个。