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Essay #18.  560    (23993-!-item-!-188;#058&00560-00)

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.

Question #59.  560-01  (24039-!-item-!-188;#058&000560-01)

The primary purpose of the passage is to

(A)   present several explanations for a well-known fact

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.

(B) suggest alternative methods for resolving a debate

(C) argue in favor of a controversial theory

(D) question the methodology used in a study

(E) discuss the implications of a research finding

答案是E，但是我的选择是A,我的理解是对古代食肉动物牙齿损坏高这种well-known fact，给出了either。。。。or这2种解释，有NN能帮我解释一下我的理解错在哪里了吗？谢谢了