OG12 RC第七题，不懂啊，求助

yaoyuanyuan

LINE 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
(5)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.
(10)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
(15) 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
(20) 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.
(25) 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.
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7.The researchers' conclusion concerning the absence
of demographic bias would be most seriously
undermined if it were found that

(A)the older an individual carnivore is, the more
likely it is to have a large number of tooth
fractures（为什么解释中说Th is statement supports
rather thanundermines the researchers’ conclusion.）

(B)the average age at death of a present-day
carnivore 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 did younger individuals

(D)the methods used to determine animals' ages in
fossil samples tend to misidentify many older
individuals as youngerindividuals

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

LeannaChina

这提示让你找个人口学统计偏差不能忽略的条件

当初为何可以忽略——原文为：老的个体在化石样本中并无高比例出现——隐含的一个原因：老个体比年轻个体牙齿磨损量大，这是个常识，就像大部分老人的牙齿都没有年轻人的好——如果老个体高比例出现，意味着古肉食动物牙齿磨损量高是因为化石样本中老个体比例高，就无法去探究别的原因了

而A的意思是：食肉动物个体越老，牙齿磨损量越多
这不就是在说老个体牙齿不好嘛，文章中又有老个体没有高比例出现，所以磨损量高就不会是因为老个体多导致的，那么A实际上是支持了文章的观点，因为它是那个观点的前提条件

yaoyuanyuan

谢谢