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.
Which of the following, if true, would most weaken the author's conclusion in highlight lines ?
这是一道weaken削弱型的逻辑推理题，先从高亮的句子中找到原文推理的假设，从假设来着手，文章提到第一种方法的unproductive和第二种方法的not succeeded就直接得出由self-regulating或者other agent的结论，文章的假设是方法不成功就是里面猜猜的原因不对，而是其他原因引起，而没有考虑方法本身在实施过程中的不合理导致的不成功。
B选项：new experiemnt有了新的结论，untried way说明是对之前实验的改进，并且实验表明habit对population cycle有影响，自然就削弱了下文说有其他因素影响的说法
C选项：这个选项只是在混淆下文的nuclear polyhedrosis virus和第一段的结论，nuclear polydedrosis virus和birds，parasites都是population cycle的factor，两者的结合并不能在逻辑上证明结论的猜想是错的
看到“in short”就知道是对前文观点的总结，那么就去看前文具体讲了什么。 ；原文：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. 一般的方法失败（例如：监测鸟、监测寄生虫）+ 改变栖息等都失败了； ；目标：削弱这个结论（找个选项能够说明有方法成功了）； ；A：新的实验显示，多种捕食L的虫子和鸟近几年都减少了；推测不出来“捕食L的虫子和鸟都减少了”是否会对“population cycle有影响”。； ；B：新实验显示，之前没有试过的方法（改变栖息地）减少了L 的生命周期；成功削弱； ；C：最近的试验表明，病毒在L的捕食者身上出现；（和试验方法无关）； ；D：不同的L物种有不同的栖息地，所以难以测评天气对pop cyc的效果；（和试验方法无关）； ；E：病毒能被观察到；（和试验方法无关）；
前提：改变caterpillars’ habitat和减少caterpillar populations，都不影响周期。--> 推出结论: 有除了predatory birds 和 parasites的其他 agent。问削弱结论，即改变前提。B. 用另一个没试过的方法改变栖息地，结果周期变短了。
结论：these insect populations at least be regulated by other factor 削弱：these insect populations are regulated by predatory birds or parasites. B：these insect populations are regulated by habitat change. habitat—predatory birds or parasites