最后再问管13 阅读 一题

      A small number of the forest

       species of lepidoptera (moths and

       butterflies, which exist as caterpillars

Line       during most of their life cycle) exhibit

  (5)      regularly recurring patterns of popu-

lation growth and decline—such

fluctuations in population are known

as population cycles.  Although many

different variables influence popula-

(10)      tion 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

(15)      considerable research.  The com-

mon approach of studying causes of

population cycles by measuring the

mortality caused by different agents,

such as predatory birds or parasites,

(20)      has been unproductive in the case of

       lepidoptera.  Moreover, population

       ecologists’ attempts to alter cycles

by changing the caterpillars’ habitat

and by reducing caterpillar popula-

(25)      tions 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

(30)      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

(35)    of caterpillars, but population ecolo-

gists had usually considered viral

disease to have contributed to the

decline once it was underway rather

than to have initiated it.  The recent

(40)     work has been made possible by

new techniques of molecular biology

that allow viral DNA to be detected

at low concentrations in the environ-

ment.  Nuclear polyhedrosis viruses

(45)      are hypothesized to be the driving

force behind population cycles in

lepidoptera in part because the

viruses themselves follow an infec-

tious cycle in which, if protected from

(50)      direct sun light, they may remain

virulent for many years in the envi-

ronment, embedded in durable

crystals of polyhedrin protein.

Once ingested by a caterpillar,

(55)      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

(60)      crystals.  These crystals reenter the

environment after the insect dies and

decomposes, thus becoming avail-

able to infect other caterpillars.

      One of the attractions of this

(65)      hypothesis is its broad applicability.

Remarkably, despite significant differ-

ences in habitat and behavior, many

species of lepidoptera have population

cycles of similar length, between eight

(70)      and eleven years.  Nuclear polyhe-

drosis viral infection is one factor these

disparate species share.

--------------------------------------------------------------------------------

Q34:

Which of the following, if true, would most weaken the author’s conclusion in lines 25-30?

New research reveals that the number of species of birds and parasites that prey on lepidoptera has dropped significantly in recent years.

New experiments in which the habitats of lepidoptera are altered in previously untried ways result in the shortening of lepidoptera population cycles.

Recent experiments have revealed that the nuclear polyhedrosis virus is present in a number of predators and parasites of lepidoptera.

Differences among the habitats of lepidoptera species make it difficult to assess the effects of weather on lepidoptera population cycles.

Viral disease is typically observed in a large proportion of the lepidoptera population.

Answer: c我b

不用看我的答案了但答案我不明白为什么选c 。

我就不会作阅读里的逻辑，每做每错。 请高手给些指点，为什么一作阅读逻辑就错？？

全文结构现象解释型：

第一段：现象及第一个解释

第二段：正确的解释

第三段：2段的解释好啊！

做逻辑题，必须看出问题的论证结构：The com-

mon approach of studying causes of

population cycles by measuring the

mortality caused by different agents,

such as predatory birds or parasites,

(20)      has been unproductive in the case of

       lepidoptera. （试验结果1，evidence 1) Moreover, population

       ecologists’ attempts to alter cycles

by changing the caterpillars’ habitat

and by reducing caterpillar popula-

(25)      tions have not succeeded.(evidence 2)  In short,

the evidence(多清楚的论证关系） implies that these insect

populations, if not self-regulating, may

at least be regulated by an agent more

intimately connected with the insect than

(30)      are predatory birds or parasites.（结论）

结论就是鸟和parasites不是主要的regulator.

削弱的目的就是鸟和parasites是主要的regulator.

现在来分析选项差别：

1. New research reveals that the number of species of birds and parasites that prey on lepidoptera has dropped significantly in recent years. (无关）
2. New experiments in which the habitats of lepidoptera are altered in previously untried ways result in the shortening of lepidoptera population cycles.（在环境evidence2和小鸟evidence1之间架了桥梁，加强）
3. Recent experiments have revealed that the nuclear polyhedrosis virus is present in a number of predators and parasites of lepidoptera. (在病毒和小鸟间架了桥。全文结论是病毒导致变化。这里说病毒来自小鸟。）
4. Differences among the habitats of lepidoptera species make it difficult to assess the effects of weather on lepidoptera population cycles. （天气无关吧，即使把天气和病毒联系起来，还是无法对这个结论削弱）
5. Viral disease is typically observed in a large proportion of the lepidoptera population.（无关）

"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."---昆虫的数量的变化更多是由其他因素决定, 而非鸟类或寄生虫.

问题要你weaken这句话, 那么就是说昆虫的数量变化更多与鸟类相关. 那么我们就看选项中那个表示这个意思, 哪怕是搭个边. 在五个选项比较中, C更能表达鸟吃虫的那种意思. 大量的鸟吃了很多感染有这种病毒的虫子. 呵呵...