og-235

235题里问........................were free of tooth breakage,........中的free当什么讲？本来不想麻烦大家来着，可是放个题不明白还是别扭

还有请问234题，我也不明白，选项D中说的“把更老的个体错误定义为更年轻的个体”那个怎么削弱作者的结论了  ？？

期待指教

free应是指“没有”的意思。

请认真看看解释吧。ETS说得够细致了。

234.

This question asks you to identify a statement that would undermine the researchers’ conclusion regarding demographic bias.本题考察 逻辑关系、名词定位 两个问题

The researchers concluded that demographic bias was not a factor because older individuals were not disproportionately represented among the fossils.  这是原文的 改写

The implication of this conclusion is that older individuals might be expected to have a higher rate of

tooth breakage. 这说明文章中需注意的 隐含意思。

The best answer is D. 给出答案。best

The researchers’ conclusions with regard to the demographic bias are depended upon reliable information about the age of the individuals in the fossil samples. 说明了 逻辑的关键点 在于年龄的分布信息。

If there were a demographic bias-in this case, a preponderance of older individuals-in the fossil samples, the misidentification of older individuals as younger ones would have concealed the bias from researchers. 指出D选项中所述的情况，即将老的个体当作新的个体，抓住了年龄分布这一关键点，揭示了确实存在统计分布偏差。

Choice A is not correct. A的错误形式比较特殊，需注意

The researchers’ conclusions imply that older individuals might be expected to have a higher rate of tooth breakage. 这再次说明文章中需注意的 隐含意思。

Findings that confirmed this would not undermine the researchers’ conclusions that the samples were representative.文章内容中已包含的隐含意思不可能对论述构成进一步的削弱作用。即文章内容的确认不能对论述本身发生额外作用。这实际上是逻辑题目中经常需要注意的问题。

The information in choice B, C and E is irrelevant to the issue of whether older individuals were disproportionately represented among the fossil sample. 与中心问题 无关

你看，它们几乎每一句都有用，都需要注意。而且复杂问题就多说几句，简单问题就一笔带过。唉，不得不佩服ETS啊。

是不是就是说：

conclusion:因为年龄大的，牙齿损坏的厉害，所以对研究有影响。

undermine:年龄大的经常被误认为成年龄小的，。。。。

the demographic bias are depended upon reliable information about the age of the individuals ，年龄判断错了不就正好说明demographic bias存在么？跟“对研究有影响”这个结论不是一样么？

还有就是这个句子不明白：The researchers concluded that demographic bias was not a factor because older individuals were not disproportionately represented among the fossils我怎么不明白这个句子的关系？？那个老的不能代表跟偏差不是一个因素有什么关系？？？？

ETS说，The researchers’ conclusions with regard to the demographic bias are depended upon reliable information about the age of the individuals in the fossil samples.他是讲The researchers’ conclusions are depended upon reliable information。而你对其主语的判断疏忽了。是吧？：）

我们已知，结论是关于the absence of demographic bias的。下一步需要定位原文the researchers dismissed demographic bias because older individuals were not overrepresented in the fossil samples。这就是说，研究者排除了可能存在的年龄分布偏差，因为在那些考古食肉动物化石样本中，年龄老的个体比例没有出现不正常的过高情况。这样，样本的年龄分布说明，因为个体年龄老而造成牙齿破损的这种可能的他因不能构成文中特殊现象的主要解释，排除了他因。要对此结论进行削弱，就是需要肯定上述在文中被排除的他因。选项D恰恰肯定了他因，构成削弱。

另外，为方便大家，将原文列出如下：

A recent study has provided clues to predator-prey dynamics in the late Pleistocene era. Researchers compared the number of tooth fractures in present-day carnivores with tooth fractures in carnivores that lived 36,000 to 10,000 years ago and that were preserved in the Rancho La Brea tar pits in Los Angeles. The breakage frequencies in the extinct species were strikingly higher than those in the present-day species.

In considering possible explanations for this finding, the researchers dismissed demographic bias because older individuals were not overrepresented in the fossil samples. They rejected preservational bias because a total absence of breakage in two extinct species demonstrated that the fractures were not the result of abrasion within the pits. They ruled out local bias because breakage data obtained from other Pleistocene sites were similar to the La Brea data. The explanation they consider most plausible is behavioral differences between extinct and present-day carnivores-in particular, more contact between the teeth of predators and the bones of prey due to more thorough consumption of carcasses by the extinct species. Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities.

234. The researchers’ conclusion concerning the absence of demographic bias would be most seriously undermined if it were found that

(A) the older as individual carnivore is, the more likely it is to have a large number of tooth fratures

(B) the average age at death of a present-day carnivores is greater than was the average age at death of a Pleistocene carnivore

(C) in Pleistocene carnivore species, older individuals consumed carcasses as thoroughly as younger individuals

(D) the methods used to determine animals’ ages in fossile samples tend to misidentify many older individuals as younger individuals

(E) data concerning the ages of fossil samples cannot provide reliable information about behavioral differences between extinct carnivores and present-day carnivores

我靠！！这下完全清楚了！！！

多谢wangyu73cn老兄的指点！！！！！！

惭愧,居然没看出这里的隐含前提: the older an individual carnivore is, the more likely it is to have a large number of tooth fractures.

跟个贴:

235. The passage suggests that if the researchers had not found that two extinct carnivore species were free of tooth breakage, the researchers would have concluded that

(A) the difference in breakage frequencies could have been the result of damage to the fossil remains in the La Brea pits

(B) the fossils in other Pleistocene sites could have higher breakage frequencies than do the fossils in the La Brea pits

(C) Pleistocene carnivore species probably behaved very similarly to one another with respect to consumption of carcass

(D) all Pleistocene carnivores species differed behaviorally from present-day carnivore species（A）

(E) predator densities during the Pleistocene era were extremely high

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请问: A中的damage是否指文章中的abrasion within the pits?