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OG20官方指南,建议同学们刷3遍。第一遍做题了解题型和考点,第二遍精刷,第三遍集中解决疑难问题。建议考生第一遍刷题采用官方正版纸质书籍,若遇到疑难问题,欢迎在此专区查阅解析,提供解析,参与题目讨论,与所有考生一起解决疑难问题。
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A small number of the forest species of lepidoptera (moths and butterflies, which exist as caterpillars during most of their life cycle) exhibit regularly recurring patterns of population growth and decline—such fluctuations in population are known as population cycles. Although many different variables influence population levels, a regular pattern such as a population cycle seems to imply a dominant, driving force. Identification of that driving force, however, has proved surprisingly elusive despite considerable research. The common approach of studying causes of population cycles by measuring the mortality caused by different agents, such as predatory birds or parasites, has been unproductive in the case of lepidoptera. Moreover, population ecologists’ attempts to alter cycles by changing the caterpillars’ habitat and by reducing caterpillar populations have not succeeded. In short, the evidence implies that these insect populations, if not self-regulating, may at least be regulated by an agent more intimately connected with the insect than are predatory birds or parasites.

Recent work suggests that this agent may be a virus. For many years, viral disease had been reported in declining populations of caterpillars, but population ecologists had usually considered viral disease to have contributed to the decline once it was underway rather than to have initiated it. The recent work has been made possible by new techniques of molecular biology that allow viral DNA to be detected at low concentrations in the environment. Nuclear polyhedrosis viruses are hypothesized to be the driving force behind population cycles in lepidoptera in part because the viruses themselves follow an infectious cycle in which, if protected from direct sunlight, they may remain virulent for many years in the environment, embedded in durable crystals of polyhedrin protein. Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells. Late in the course of the infection, millions of new virus particles are formed and enclosed in polyhedrin crystals. These crystals reenter the environment after the insect dies and decomposes, thus becoming available to infect other caterpillars.

One of the attractions of this hypothesis is its broad applicability. Remarkably, despite significant differences in habitat and behavior, many species of lepidoptera have population cycles of similar length, between eight and 11 years. Nuclear polyhedrosis viral infection is one factor these disparate species share.

【OG20-P431-538题】

It can be inferred from the passage that while inside its polyhedrin protein crystals, the nuclear polyhedrosis virus

  • 分析A选项
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  • 分析B选项
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  • 分析C选项
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  • 分析D选项
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  • 分析E选项
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该题目由网友nN9YLN提供。更多GMAT题目请
暂无雷哥网文字解析
当前版本由 你是风儿 更新于2015-11-17 16:42:05 感谢由 你是风儿 对此题目的解答所做出的贡献。

这是一道明显的推断题,我们首先根据关键字 the nuclear polyhedrosis virus定位到原文第二段:Nuclear polyhedrosis viruses are hypothesized to be...这段话说的是 nuclear polyhedrosis viruses对population cycle的作用


A选项:原文中说的是如果没有暴露在光线中,他们会在环境中保持virulent多年,保持crystal状态,一旦被虫吃掉,这种病毒的crystal就会解题。题目问的是当nuclear polyhedrosis virus inside crystal的时候,那就是crystal状态,往前看原文就是protected from direct sunlight,而不是题目中的exposed to


B选项:原文没有提到attractive to predators信息


C选项:原文中提到, "Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells." 这是的crystal已经dissolve了,不可能是题目中的inside crystal


D选项:原文提到可以ingest by caterpillar, "Once ingested by a caterpillar"


E选项:定位new techniques的原文"The recent work has been made possible by new techniques of molecular biology that allow viral DNA to be detected"


题目讨论 4条评论)

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    245240abh

    Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells.
    dissolve才release了感染  所以没有之前肯定没有感染
    0 0 回复 2020-09-18 20:15:57
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    emily666

    文字游戏。。。唉
    0 0 回复 2020-03-16 19:27:08
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    511734aqj

    这个题真的狡猾 人家问的是virus在crystal里面的状况 virus在crystal resolve以后再发挥作用 所以肯定是C
    0 0 回复 2019-12-24 16:55:54
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    千千

    while 这里表示当。。。时 不是表示转折和对比
    当P在crystal 里时怎样?
    原文说 crystal溶解后,释放p然后感染细胞
    那也就是说当p还在crystal里面即crystal未溶解时不能感染细胞
    其他几个选项都没有依据 或者与事实相反(D)
    1 0 回复 2017-11-13 18:49:58
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