Thevastgrasslands of the High Plains in the central United States were settled by farmers and ranchers in the 1880s. Thisregionhas asemiaridclimate, and for 50 years after itssettlement, it supported a low-intensity agriculturaleconomyofcattleranching and wheat farming. In the early twentiethcentury, however, it was discovered that much of the High Plains was underlain by a hugeaquifer(a rocklayercontaining large quantities ofgroundwater). Thisaquiferwas named the Ogallalaaquiferafter the Ogallala Sioux Indians, who once inhabited the region

The Ogallalaaquiferis a sandstoneformationthat underlies some 583,000squarekilometers of land extending from northwestern Texas to southern South Dakota. Water from rains andmeltingsnows has been accumulating in the Ogallala for the past 30,000 years. Estimatesindicatethat theaquifercontains enough water to fill Lake Huron, butunfortunately, under thesemiaridclimaticconditions that presently exist in theregion, rates ofadditionto theaquiferareminimal, amounting to about half a centimeter a year.

The first wells were drilled into the Ogallala during thedroughtyears of the early 1930s. The ensuing rapidexpansionofirrigationagriculture, especially from the 1950s onward, transformed theeconomyof theregion. More than 100,000 wells now tap the Ogallala. Modernirrigationdevices, eachcapableof spraying 4.5 million liters of water a day, have produced alandscapedominated by geometric patterns ofcirculargreen islands of crops. Ogallala water has enabled the High Plainsregiontosupplysignificantamounts of the cotton, sorghum, wheat, and corn grown in the United States. Inaddition, 40 percent of American grain-fed beefcattleare fattened here.

Thisunprecedenteddevelopmentof afinitegroundwaterresourcewith an almostnegligiblenaturalrechargerate—that is,virtuallyno natural watersourcetoreplenishthe watersupply—has caused water tables in theregionto falldrastically. In the 1930s, wells encounteredplentifulwater at a depth of about 15 meters; currently, they must be dug to depths of 45 to 60 meters or more. In places, the water table is declining at arateof a meter a year, necessitating theperiodicdeepening of wells and the use of ever-more-powerful pumps. It is estimated that atcurrentwithdrawal rates, much of theaquiferwill run drywithin40 years. The situation is mostcriticalin Texas, where theclimateis driest, the greatestamountof water is being pumped, and theaquifercontains theleastwater. It is projected that theremainingOgallala water will, by the year 2030, support only 35 to 40 percent of the irrigatedacreagein Texas that is supported in 1980.

Thereactionof farmers to theinevitabledepletion of the Ogallala varies.

Many have been attempting toconservewater by irrigating less frequently or by switching to crops

thatrequireless water. Others, however, have adopted thephilosophythat it is best to use the water while it is stilleconomicallyprofitableto do so and toconcentrateon

high-value crops such as cotton. Theincentiveof the farmers who wish toconservewater is reduced by their knowledge that many of their neighbors are profiting by using great amounts of water,

and in theprocessare drawing down the entireregion’s water supplies.

In the face of the upcoming watersupplycrisis, a number of grandiose schemes have been developed totransportvastquantities of water bycanalor pipeline from the Mississippi, the Missouri, or the Arkansas rivers. Unfortunately, thecostof water obtainedthroughany of these schemes would increase pumping costs atleasttenfold, making thecostof irrigated agricultural products from theregionuncompetitive on the national and international markets. Somewhatmorepromisinghave been recent experiments for releasing capillary water (water in the soil) above the water table by injecting compressedairinto the ground. Evenif thisprocessproves successful, however, it would almost triple water costs. Geneticengineeringalso may provide apartialsolution, as new strains of drought-resistant crops continue to be developed. Whatever the final answer to the water crisis may be, it isevidentthatwithinthe High Plains,irrigationwater will never again be theabundant, inexpensiveresourceit was during the agriculturalboomyears of the mid-twentiethcentury.

Questions:
question_stem: According to paragraph 1, which of the following statements about the High Plains is true?
choices: tag: A
text: Until farmers and ranchers settled there in the 1880s, the High Plains had never been inhabited.

tag: B
text: The climate of the High Plains is characterized by higher-than-average temperatures.

tag: C
text: The large aquifer that lies underneath the High Plains was discovered by the Ogallala Sioux Indians.

tag: D
text: Before the early 1900s there was only a small amount of farming and ranching in the High Plains.
answer_key: D
explanation: 排除法，以1880s 做关键词定位至第一句，说1880s 农牧民定居在 High Plains，没说1880前没有人，A 错：The vast grasslands of the High Plains in the central United States were settled by farmers and ranchers in the 1880s.以 climate 做关键词定位至第二句，原文说 semiarid，没说温度，B 错；D 中 small amount of farming and ranching 和原文第二句中的 low-intensity 是同义替换，选。This region has a semiarid climate, and for 50 years after its settlement, it supported a low-intensity agricultural economy of cattle ranching and wheat farming.以人名做关键词定位至最后一句，说这个人是 inhibit 在这儿的，没说是他发现的，C 错：This aquifer was named the Ogallala aquifer after the Ogallala Sioux Indians, who once inhabited the region.

question_stem: According to paragraph 2, all of the following statements about the Ogallala aquifer are true EXCEPT:
choices: tag: A
text: The aquifer stretches from South Dakota to Texas.

tag: B
text: The aquifer’s water comes from underground springs.

tag: C
text: Water has been gathering in the aquifer for 30,000 years.

tag: D
text: The aquifer’s water is stored in a layer of sandstone.
answer_key: B
explanation: A 以两个地名，D 以 sandstone 做关键词定位至第一句，A 和 D 都对，不选：The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to southern South Dakota.C 以30000 years 做关键词定位至第二句，C 对，不选：Water from rains and melting snows has been accumulating in the Ogallala for the past 30,000 years.从这句话同时可以看到地下水是来自 rain and melting snow，不是泉水，所以 B 错，选。

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: Despite the current impressive size of the Ogallala aquifer, the region’s climate keeps the rates of water addition very small.

tag: B
text: Although the aquifer has been adding water at the rate of only half a centimeter a year, it will eventually accumulate enough water of fill Lake Huron.

tag: C
text: Because of the region’s present climatic conditions, water is being added each year to the aquifer.

tag: D
text: Even when the region experiences unfortunate climatic conditions, the rates of addition of water continue to increase.
answer_key: A
explanation: A, 文的结构是估计水很多，足以填满休伦湖，但在半干旱天气下，补充的少。主要逻辑是转折，转折之后是重点强调内容。A 答案完整地反映了这两个方面，正确；B 强调的点搞反，原句强调的是补充的少，B 强调的是现在的量大；C 的 added 和原句不符，而且遗漏了主要的内容；D 说补充的持续增长，原文没说。

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

tag: B
text: surprising

tag: C
text: initial

tag: D
text: subsequent
answer_key: D
explanation: ensue 跟随，接下来，所以 subsequent 是答案。原文说第一批水井是1930s 挖掘的，ensuing 所在的那句话又说1950s 什么样的农业的快速扩张，这两个时间说明动作是有先后的，而且 first 一般必然有下文的，所以应该是接着的。注意 continuing 是个很大的迷惑项，继续是指一个动作的延续，而接下来是两件事情接着发生，B 令人吃惊和 C 最初的，起始的都不对。

question_stem: In paragraph 3, why does the author provide the information that 40 percent of American cattle are fattened in the High Plains?
choices: tag: A
text: To suggest that crop cultivation is not the most important part of the economy of the High Plains

tag: B
text: To indicate that not all economic activity in the High Plains is dependent on irrigation

tag: C
text: To provide another example of how water from the Ogallala has transformed the economy of the High Plains

tag: D
text: To contrast cattle-fattening practices in the High Plains with those used in other region of the United States
answer_key: C
explanation: 功能目的题，40%明显是一个例子，往前看，说这个地方的水养活了 high plains 地区的很多农作物，in addition 说明进一步，也就是除了农业还有牧业，所以是 C，provide another example，没有说农业和牧业谁重要，A 错；牧业确实不依赖灌溉，但也依赖这个地方的水，所以 B 无关；没有对比，D 错。

question_stem: The word “unprecedented” in the passage is closest in meaning to
choices: tag: A
text: difficult to control

tag: B
text: without any restriction

tag: C
text: unlike anything in the past

tag: D
text: rapidly expanding
answer_key: C
explanation: unprecedented: 史无前例的，un 表示没有，pre 前，想到 precede，在……之前。A 是很难控制；B 是没有限制；C 是和过去的任何东西都不同；D 是快速扩张。根据词意，C 正确。对应原文：This unprecedented development of a finite groundwater resource with an almost negligible natural recharge rate—that is, virtually no natural water source to replenish the water supply—has caused water tables in the region to fall drastically.A 难以控制和 B 毫无限制都有轻微贬义，而原词只是在叙述一个事实，属中性。D 快速扩张也不沾边，而且 A/B/D 三个选项在意思上有共同点，唯独 C 不同，只要知道 pre 是前就一定能选出答案。

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

tag: B
text: perhaps

tag: C
text: frequently

tag: D
text: almost
answer_key: D
explanation: virtually 几乎。注意 virtual 有虚拟和真实两个截然相反的意思，破折号之前说 negligible recharge rate，补给可以忽略，就是很少，但还是有的，后面解释说什么没有水补充，如果选除了 almost 之外的三项，都说明可能没水，与原文意思不符。

question_stem: According to paragraph 4, all of following are consequences of the heavy use of the Ogallala aquifer for irrigation EXCEPT:
choices: tag: A
text: The recharge rate of the aquifer is decreasing.

tag: B
text: Water tables in the region are becoming increasingly lower.

tag: C
text: Wells now have to be dug to much greater depths than before.

tag: D
text: Increasingly powerful pumps are needed to draw water from the aquifer.
answer_key: A
explanation: 排除法，分别以 recharge rate，water tables，wells，powerful pumps 做关键词定位至本段前三句：In places, the water table is declining at a rate of a meter a year, necessitating the periodic deepening of wells and the use of ever-more-powerful pumps.B/C/D 三项在原文中都有说，而 A 的 recharge rate 在第一句中提到，但不是 heavy use 的结果，所以 A 错，选。而且跳出这道题看，随着地下水位的下降，井必须打得更深，水泵必须功率更大，这是一系列的因果关系，只有 A 不是这个因果序列中的。

question_stem: According to paragraph 4, compared with all other states that use Ogallala water for irrigation, Texas
choices: tag: A
text: has the greatest amount of farmland being irrigated with Ogallala water

tag: B
text: contains the largest amount of Ogallala water underneath the soil

tag: C
text: is expected to face the worst water supply crisis as the Ogallala runs dry

tag: D
text: uses the least amount of Ogallala water for its irrigation needs
answer_key: C
explanation: 以 Texas 为关键词定位至倒数第二句，说德州气候最干燥，地下水最少，面临的问题最严峻，C 是原文的同义改写。

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

tag: B
text: predictable

tag: C
text: unavoidable

tag: D
text: final
answer_key: C
explanation: inevitable: 不可避免的，必然的。A 是不幸的；B 意为可预测的；C 是不可避免的；D 是最终的。根据词意，C 正确。对应原文：The reaction of farmers to the inevitable depletion of the Ogallala varies.上段整个都在说地下水位在剧烈下降，depletion 指的是水用光，承上启下应该是地下水一定会用光，作者只是在陈述事实，没有好坏之说，所以 unfortunate 不对，不要主观猜想水没了对当地人一定不好；predictable 可预见的也不对，因为原文没给出任何预见性的信息；就单词本身看，in 前缀表示否定，所以必须答案也有类似的部分，unavoidable 无疑是最好的选项。

question_stem: Paragraph 5 mentions which of the following as a source of difficulty for some farmers who try to conserve water?
choices: tag: A
text: Crops that do not need much water are difficult to grow in the High Plains.

tag: B
text: Farmers who grow crops that need a lot of water make higher profits.

tag: C
text: Irrigating less frequently often leads to crop failure.

tag: D
text: Few farmers are convinced that the aquifer will eventually run dry.
answer_key: B
explanation: 以 some farmers who try to conserve water 为关键词定位至最后一句，说那些不省水的农民因为没有节约水获得利润，众多选项中只有 B 提到了利润问题，是正确答案。

question_stem: According to paragraph 6, what is the main disadvantage of the proposed plans to transport river water to the High Plains?
choices: tag: A
text: The rivers cannot supply sufficient water for the farmer’s needs.

tag: B
text: Increased irrigation costs would make the products too expensive.

tag: C
text: The costs of using capillary water for irrigation will increase.

tag: D
text: Farmers will be forced to switch to genetically engineered crops.
answer_key: B
explanation: 以 transport water 做关键词定位至本段第一句，第二句开始的 unfortunately 清楚的表明了这句话会说一个运水产生的问题，就是成本太贵，使产品价格失去竞争力，B 和 C 提到成本，而只有 B 提到了产品价格升高，正确。