Around 1870, a little fruit-eatinginsectarrived in San Jose, California, on some nurserystockshipped from Asia. Thepest, which became known as the San Josescale, quicklyspreadthroughthe United States and Canada, killingorchardtrees as it went. Farmers found that the best way to control thescalewas tospraytheir orchards with a mixture ofsulfurandlime. Withina few weeks of spraying a tree, theinsectvanishedcompletely.

Around the turn of thecentury, however, farmers began to notice that the sulfur-lime mixture was not working all that well. Ahandfulof scales wouldsurvivea spraying andeventuallyrebound to theirformernumbers. In ClarkstonValleyin WashingtonState,orchardgrowers became convinced that manufacturers were adulterating theirpesticide. They built their own factory toguaranteeapurepoison, which they drenched over their trees, yet thescalekept spreading uncontrollably. Anentomologistnamed A. L. Melander inspected the trees and found scales living happily under a thickcrustof driedspray.

Melander began tosuspectthat adulteration was not to blame. In 1912, he compared howeffectivethe sprays were in different parts of Washington. In Yakima and Sunnyside, he found that sulfur-lime couldwipeout every lastscaleon a tree, while in Clarkston between 4 and 13 percent survived. On the other hand, the Clarkston scales were annihilated by a differentpesticidemade fromfueloil, just as the insects in other parts of Washington were. In other words, the scales of Clarkston had apeculiarresistanceto sulfur-lime.

Melander wondered why. He knew that if individuals eat small amounts of certain poisons, such asarsenic, they can build up animmunity. But San Jose scales bred so quickly that no singlescaleexperienced more than a singlesprayof sulfur-lime, giving them nochanceto developimmunity.

Aradicalidea occurred to Melander. Perhaps mutations made a few scalesresistantto sulfur-lime. When farmers sprayed their trees, theseresistantscales survived, as did a few nonresistant ones that hadn’t received afataldose. The surviving scales would thenbreed, and theresistantgenes would become morecommonin the following generations. Depending on the proportions of the survivors, the trees might become covered byresistantor nonresistant scales. In the ClarkstonValleyregion, farmers had been using sulfur-lime longer than anywhere else in the Northwest and were desperately soaking their trees with thestuff. In theprocess, they were driving theevolutionof moreresistantscales.

Melander offered his ideas in 1914, but no one paid muchattentionto him; they were too busy discoveringevenmore powerful pesticides. In 1939 the Swiss chemist Paul Müller found that acompoundofchlorineand hydrocarbons called DDT could kill insects more effectively than anypreviouspesticidehad. DDT was cheap and easy to make, it could kill manyspeciesof insects, and it wasstableenough to be stored for years. It could be used in small doses, and it didn’tseemtoposeany health risks to humans. Between 1941 and 1976, 4.5 million tons of DDT were produced. DDT was so powerful and cheap that farmers gave up old-fashioned ways of controlling pests, such as draining standing water orbreedingresistantstrains of crops.

DDT andsimilarpesticides created the delusion that pests could be not merely controlled but eradicated, so farmers began spraying pesticides on their crops as a matter ofcourse, rather than to control outbreaks. Meanwhile, public health workers saw in DDT the hope of controlling mosquitoes, whichspreaddiseases such asmalaria.

DDT certainly saved a great many lives and crops, butevenin its early days, some scientists saw signs of its doom. In 1946 Swedish scientists discovered houseflies that could no longer be killed with DDT. Houseflies in other countries becameresistantas well in later years, and soon otherspeciescouldwithstandit. Melander’s warning was becoming a reality. By 1992 more than 500specieswereresistantto DDT, and the number is still climbing. As DDT began to fail, farmers at first just applied more of it; when more no longer worked, they switched to newer pesticides.

Questions:
question_stem: The word “vanished” in the passage is closest in meaning to
choices: tag: A
text: recovered

tag: B
text: disappeared

tag: C
text: adapted

tag: D
text: retreated
answer_key: B
explanation: 前文是 the best way to control the scale，所在句是前一句随时间推移顺序性结论，所以 vanished= control；下文说 however, farmers began to notice that the sulfur-lime mixture was not working all that well. A handful of scales would survive a spraying and eventually rebound 与词汇题所在句构成转折；下文说有一些存活、反弹，那么词汇题所在句应该是没存活的、没反弹的，联系上文控制住了那应该是消失了，AC 错； D 的 retreated 是 an act or process of withdrawing especially from what is difficult, dangerous, or disagreeable 一般指撤军，或从困难危险中撤离，色彩在此不对，所以 B。

question_stem: According to paragraph 2, how did farmers in Clarkston Valley explain the lack of success they were having with the use of the sulfur-lime mixture?
choices: tag: A
text: They suspected that surviving insects might have been a different variety of scale.

tag: B
text: They believed that the mixture was not being applied to the trees properly.

tag: C
text: They thought the mixture was being weakened by the manufacturers.

tag: D
text: They assumed that the new scales were coming from nearby orchards.
answer_key: C
explanation: 看好题干：是问农民的想法，所以与农民有关的是 P2的1和2句；1是发现反弹现象，2是他们的想法，也是题干定位所在 In Clarkston Valley in Washington State, orchard growers became convinced that manufacturers were adulterating their pesticide. In Clarkston Valley in Washington State, orchard growers = They= farmers in Clarkston Valley ；adulterating（掺杂掺假）= was being weakened； pesticide= the mixture； manufacturers= manufacturers。事实题要证据不能推理，ABD 文中未提，所以 C。

question_stem: In paragraph 3, why does the author compare the effects of sulfur-lime pesticide in Yakima and Sunnyside with its effect in Clarkston?
choices: tag: A
text: To provide evidence that a new pesticide made from fuel oil was more effective than the sulfur-lime mixture

tag: B
text: To explain why Melander thought that scales had become resistant to the pesticide

tag: C
text: To indicate how Melander discovered that scale insects were killing trees throughout Washington

tag: D
text: To illustrate the success of farmers who chose to manufacture their own pesticide
answer_key: B
explanation: why does the author compare…? why does the author mention…? 这类题干是目的题，问观点。题干中的比较是3段段内细节内容，段段意即观点在首尾，所以是首尾解题。B 是尾句改写，所以 B。

question_stem: According to paragraph 4, why did Melander reject the possibility that scales could have developed immunity?
choices: tag: A
text: Immunity could not effectively be passed on to the enormous number of offspring produced by scales.

tag: B
text: The development of immunity to a poison usually occurs from eating small doses of the poison, but scales did not eat the sulfur-lime mixture.

tag: C
text: The lifecycle of a scale is so short that no scale was exposed to more than one spraying of pesticide.

tag: D
text: Only certain poisons lead to the development of an immunity, and the poisons used in the pesticides were not believed to be among these.
answer_key: C
explanation: 事实题。why 问因果，reject 对应文章否定/转折，及 developed immunity，指向解题句为 But San Jose scales bred so quickly that no single scale experienced more than a single spray of sulfur-lime, giving them no chance to develop immunity. C 为词句改写，The lifecycle of a scale is so short = San Jose scales bred so quickly；no scale was exposed to more than one spraying of pesticide= no single scale experienced more than a single spray of sulfur-lime，所以 C。

question_stem: According to paragraph 5, how did Melander account for the increasing number of scales that were resistant?
choices: tag: A
text: A few scales developed mutated genes that gave them pesticide resistance, and these genes were then spread among later generations.

tag: B
text: Farmers were using so much pesticide that only resistant scales could survive and reproduce.

tag: C
text: Some scales that survived the pesticide did not have a genetic mutation for resistance and their numbers made it appear that scales were becoming increasingly resistant.

tag: D
text: Scales receiving several low doses of pesticide over the course of their lives gradually built up an immunity.
answer_key: A
explanation: 注意：题干中 account for 是解释的意思，实际全段都在为前面3、4段解释 scales 出现的原因；但如果没有按上下文解，用定位方法解，那应该定位在本段最后一句，因为 driving 导致表因果=account for；more resistant scales 等于题干中的 increasing number of scales，所以5段结尾是结果。那么5段前面信息是在解释，然后在结尾归出结果。A 是对5段前面信息的改写，所以 A。

question_stem: What can be inferred from paragraph 5 about resistance to sulfur-lime pesticide in regions of the Northwest other than Clarkston?
choices: tag: A
text: The proportion of resistant scales was lower in the other regions because they used several pesticides not used in Clarkston.

tag: B
text: The proportion of resistant scales was lower in the other regions because they had not used sulfur-lime pesticide as long as Clarkston had.

tag: C
text: The scales in the other regions could not develop resistance because they were genetically different from the scales in Clarkston.

tag: D
text: The scales in the other regions could not develop resistance because they were never exposed to the sulfur-lime pesticide.
answer_key: B
explanation: 推理题。Northwest other than Clarkston，2者比较 到原文定位；5段后两句解题，属于逆向推理，取最后两句话相反解题 In the Clarkston Valley region, farmers had been using sulfur-lime longer than anywhere else in the Northwest and were desperately soaking their trees with the stuff. In the process, they were driving the evolution of more resistant scales. Clarkston 地用 sulfur-lime longer than anywhere else，导致 more resistant scales；其他地用的比 Clarkston 地少，所以 resistant scales 少，所以 B。

question_stem: All of the following are mentioned in paragraph 6 as true of DDT EXCEPT:
choices: tag: A
text: It could be manufactured at a low cost.

tag: B
text: It was effective against many different species.

tag: C
text: It did not need to be used in large doses in order to be effective.

tag: D
text: It had been used successfully in Europe before 1939.
answer_key: D
explanation: 问 DDT。到原文定位多处，所以4个选项到原文定位 low cost= cheap；effective against many different species = could kill insects more effectively，kill many species of insects；not need to be used in large doses= used in small doses；used successfully in Europe before 1939，1939才发现；Between 1941 and 1976才被农民用；1939前没用过且更没有 successfully，所以 D。

question_stem: According to the passage, in what way did sulfur-lime and DDT have similar histories of use?
choices: tag: A
text: With both pesticides users at first had the false belief that the pesticide would completely eliminate pests.

tag: B
text: In both cases it was found that widespread use of the pesticide caused health problems in humans.

tag: C
text: Both pesticides were eventually used only in small quantities to avoid the development of resistance to the pesticide.

tag: D
text: Users of both pesticides had the mistaken belief that the pesticide could be used to control diseases affecting humans, such as malaria.
answer_key: A
explanation: 关联事实题。按题干找到 sulfur-lime 和 DDT 并找到 similar。解题句为：DDT and similar pesticides（前文的 sulfur-lime）created the delusion(=false belief) that pests could be not merely controlled but eradicated(=completely eliminate)… 所以 A。