『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 57 Passage 1阅读练习：According to paragraph 5, how did Melander account for the increasing number of scales that were resistant?真题题目及答案解析，TPO/Official 57 Passage 1阅读原文范文音频翻译

托福TPO/Official 57 Passage 1阅读原文According to paragraph 5, how did Melander account for the increasing number of scales that were resistant?题目答案及解析-新东方托福官方网校手机版

大约在1870年，一只吃水果的小昆虫随着从亚洲运来的苗木来到了加利福尼亚州的圣何塞。

Around 1870, a little fruit-eating insect arrived in San Jose, California, on some nursery stock shipped from Asia.

这种后来被称为“梨园蚧”的害虫迅速蔓延到美国和加拿大，一路上祸害了果园里的树木。

The pest, which became known as the San Jose scale, quickly spread through the United States and Canada, killing orchard trees as it went.

农民们发现控制它们的最好方法是在果园里喷洒硫和石灰的混合物。

Farmers found that the best way to control the scale was to spray their orchards with a mixture of sulfur and lime.

对果树喷洒几周后，这种害虫就完全消失了。

Within a few weeks of spraying a tree, the insect vanished completely.

然而，在本世纪初期，农民们开始注意到硫磺和石灰的混合物并不那么有效。

Around the turn of the century, however, farmers began to notice that the sulfur-lime mixture was not working all that well.

少量的梨园蚧能够在喷洒后存活下来，并最终恢复到原来的数量。

A handful of scales would survive a spraying and eventually rebound to their former numbers.

在华盛顿州的克拉克斯顿山谷，果园种植者确信是制造商在他们的农药中掺假。

In Clarkston Valley in Washington State, orchard growers became convinced that manufacturers were adulterating their pesticide.

他们建立了自己的工厂，以保证生产出的纯净的毒药能够浇透他们的果树，但梨园蚧仍在失控地蔓延。

They built their own factory to guarantee a pure poison, which they drenched over their trees, yet the scale kept spreading uncontrollably.

一位名叫A.L. Melander的昆虫学家检查了这些树，发现蚧虫快乐地生活在一层厚厚的干燥雾壳下。

An entomologist named A.L. Melander inspected the trees and found scales living happily under a thick crust of dried spray.

梅兰德开始怀疑农药掺假不是罪魁祸首。

Melander began to suspect that adulteration was not to blame.

1912年，他比较了这些喷剂在华盛顿不同地区的使用效果。

In 1912, he compared how effective the sprays were in different parts of Washington.

在亚基马和桑尼赛德，他发现，硫石灰混合物可以消灭树上所有蚧虫，而在克拉克斯顿，却有4%到13%的蚧虫幸存下来。

In Yakima and Sunnyside, he found that sulfur-lime could wipe out every last scale on a tree, while in Clarkston between 4 and 13 percent survived.

另一方面，克拉克斯顿的蚧虫是被另一种由石油制成的杀虫剂消灭的，就像华盛顿其他地区的蚧虫一样。

On the other hand, the Clarkston scales were annihilated by a different pesticide made from fuel oil, just as the insects in other parts of Washington were.

换句话说，克拉克斯顿的蚧虫对硫石灰混合物产生了一种特殊的抵抗力。

In other words, the scales of Clarkston had a peculiar resistance to sulfur-lime.

他知道，如果一个人吃少量的某种毒物，如砷，他们可以增强免疫力。

He knew that if individuals eat small amounts of certain poisons, such as arsenic, they can build up an immunity.

但是圣何塞蚧虫繁殖得很快，这导致没有一只蚧虫经历过硫石灰混合物喷射，它们没有机会产生免疫力。

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.

梅兰德想到了一个激进的主意。

也许是基因突变使一些蚧虫对硫石灰混合物产生了抗药性。

Perhaps mutations made a few scales resistant to sulfur-lime.

当农民喷洒农药时，这些抗药蚧虫存活了下来，就如没有抗药性的蚧虫接触到非致死量的硫石灰一样存活了下来。

When farmers sprayed their trees, these resistant scales survived, as did a few nonresistant ones that hadn't received a fatal dose.

幸存下来的蚧虫进行繁殖，抗药性基因会在后代中变得更为普遍。

The surviving scales would then breed, and the resistant genes would become more common in the following generations.

根据幸存者的比例，这些树可能会被抗药性或非抗药性蚧虫覆盖。

Depending on the proportions of the survivors the trees might become covered by resistant or nonresistant scales.

在克拉克斯顿山谷地区，农民使用硫石灰的时间比西北任何地方都长，他们拼命地用硫石灰浸泡树木。

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.

在这个过程中，它们推动蚧虫向更有抵抗力的方向进化。

In the process, they were driving the evolution of more resistant scales.

1914年，梅兰德提出了他的观点，但没有人注意到他; 他们忙着探索更有效的杀虫剂。

Melander offered his ideas in 1914, but no one paid much attention to him; they were too busy discovering even more powerful pesticides.

1939年，瑞士化学家保罗·穆勒(Paul Muller)发现，一种由氯和碳氢化合物组成的DDT比以往任何杀虫剂都有效。

In 1939 the Swiss chemist Paul Muller found that a compound of chlorine and hydrocarbons called DDT could kill insects more effectively than any previous pesticide had.

DDT既便宜又容易制造，它可以杀死多种昆虫，而且它足够稳定，可以储存多年。

DDT was cheap and easy to make, it could kill many species of insects, and it was stable enough to be stored for years.

它可以小剂量使用，而且似乎不会对人类构成任何健康危害。

It could be used in small doses, and it didn't seem to pose any health risks to humans.

在1941年到1976年间，人们生产了450万吨DDT。

Between 1941 and 1976,.4.5 million tons of DDT were produced.

DDT是如此强大且廉价，以至于农民放弃了控制害虫的老旧方法，如排水或培育抗虫害的作物品种。

DDT was so powerful and cheap that farmers gave up old-fashioned ways of controlling pests, such as draining standing water or breeding resistant strains of crops.

DDT和类似的杀虫剂创造了这样的错觉,它们不仅可以控制害虫还可以根治害虫，因此农民们开始理所当然地喷洒农药,而不控制害虫爆发。

DDT and similar pesticides created the delusion that pests could be not merely controlled but eradicated so farmers began spraying pesticides on their crops as a matter of course, rather than to control outbreaks.

同时,公共卫生工作者在DDT中看到控制蚊子的希望,因为它们传播疾病,如疟疾。

Meanwhile, public health workers saw in DDT the hope of controlling mosquitoes, which spread diseases such as malaria.

DDT确实挽救了许多生命和作物，但即使在它出现初期，一些科学家预料到了它的消逝。

DDT certainly saved a great many lives and crops, but even in its early days, some scientists saw signs of its doom.

1946年，瑞典科学家发现无法被DDT杀死的家蝇。

In 1946 Swedish scientists discovered houseflies that could no longer be killed with DDT.

后来其他国家的家蝇也产生了抗药性，而很快其他物种也对它产生了抗药性。

Houseflies in other countries became resistant as well in later years, and soon other species could withstand it.

Melander's warning was becoming a reality.

到1992年，超过500种物种对DDT有抗药性，而且这个数字还在增加。

By 1992 more than 500 species were resistant to DDT, and the number is still climbing.

当DDT开始失效时，农民只是加大剂量，而当加大剂量仍然不起作用后，他们就转而使用新的杀虫剂。

As DDT began to fail, farmers at first just applied more of it;when more no longer worked, they switched to newer pesticides.

The word "vanished" in the passage is closest in meaning to

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?

In paragraph 3, why does the author compare the effects of sulfur-lime pesticide in Yakima and Sunnyside with its effect in Clarkston?

According to paragraph 4, why did Melander reject the possibility that scales could have developed immunity?

According to paragraph 5, how did Melander account for the increasing number of scales that were resistant?

What can be inferred from paragraph 5 about resistance to sulfur-lime pesticide in regions of the Northwest other than Clarkston?

All of the following are mentioned in paragraph 6 as true of DDT EXCEPT:

According to the passage, in what way did sulfur-lime and DDT have similar histories of use?

Look at the four squares  that indicate where the following sentence could be added to the passage. These advantages made it appear to be the perfect solution, and farmers began to use it in large quantities.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Pests and Pesticides Around 1870, a little fruit-eating insect arrived in San Jose, California, on some nursery stock shipped from Asia. The pest, which became known as the San Jose scale, quickly spread through the United States and Canada, killing orchard trees as it went. Farmers found that the best way to control the scale was to spray their orchards with a mixture of sulfur and lime. Within a few weeks of spraying a tree, the insect vanished completely. Around the turn of the century, 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 to their former numbers. In Clarkston Valley in Washington State, orchard growers became convinced that manufacturers were adulterating their pesticide. They built their own factory to guarantee a pure poison, which they drenched over their trees, yet the scale kept spreading uncontrollably. An entomologist named A. L. Melander inspected the trees and found scales living happily under a thick crust of dried spray. Melander began to suspect that adulteration was not to blame. In 1912, he compared how effective the sprays were in different parts of Washington. In Yakima and Sunnyside, he found that sulfur-lime could wipe out every last scale on a tree, while in Clarkston between 4 and 13 percent survived. On the other hand, the Clarkston scales were annihilated by a different pesticide made from fuel oil, just as the insects in other parts of Washington were. In other words, the scales of Clarkston had a peculiar resistance to sulfur-lime. Melander wondered why. He knew that if individuals eat small amounts of certain poisons, such as arsenic, they can build up an immunity. 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. A radical idea occurred to Melander. Perhaps mutations made a few scales resistant to sulfur-lime. When farmers sprayed their trees, these resistant scales survived, as did a few nonresistant ones that hadn’t received a fatal dose. The surviving scales would then breed, and the resistant genes would become more common in the following generations. Depending on the proportions of the survivors, the trees might become covered by resistant or nonresistant scales. 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. Melander offered his ideas in 1914, but no one paid much attention to him; they were too busy discovering even more powerful pesticides. In 1939 the Swiss chemist Paul Müller found that a compound of chlorine and hydrocarbons called DDT could kill insects more effectively than any previous pesticide had. DDT was cheap and easy to make, it could kill many species of insects, and it was stable enough to be stored for years. It could be used in small doses, and it didn’t seem to pose any 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 or breeding resistant strains of crops. DDT and similar pesticides created the delusion that pests could be not merely controlled but eradicated, so farmers began spraying pesticides on their crops as a matter of course, rather than to control outbreaks. Meanwhile, public health workers saw in DDT the hope of controlling mosquitoes, which spread diseases such as malaria. DDT certainly saved a great many lives and crops, but even in 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 became resistant as well in later years, and soon other species could withstand it. Melander’s warning was becoming a reality. By 1992 more than 500 species were resistant to 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.