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标题: 再请教一道题！！！ [打印本页]

作者: winnieqh 时间: 2009-7-23 15:06
标题: 再请教一道题！！！

a major chemical spill occurred five years ago at Baker's Beach, the world's sole nesting ground for Merrick sea turtles, and prevented nearly all the eggs laid that year form hatching. yet the number of adult female Merricks returning to lay their eggs at Baker's Beach has actually increased somewhat since five years ago. Clearly, environmentalists' prediction that the world's Merrick population would decline as a result of the spill has proven unfounded.

which of the following, if true, most seriously undermines the argument offered in refutation of the environmentalists' prediction?

a. the chemical spill five years ago occurred at a time when there were neither Merrick see turtles nor Merrick sea turtle eggs on Baker's Beach.

b. female Merrick sea turtles begin returning to Baker's Beach to lay their eggs when they are ten years old.

c. under normal conditions, only a small proportion of hatching female Merrick sea turtles survive in the ocean until adulthood and return to lay their eggs at Baker's Beach.

d. environmental pressures unrelated to the chemical spill have caused a significant decline in the population of one of the several species of sea birds that prey on Merrick sea turtle eggs.

e. after the chemical spill, an environmental group rejected a proposal to increase the Merrick sea turtle population by transferring eggs from Baker's Beach to nearby beaches that had not been affected by the spill

答案为B。为什么呢？？

作者: winnieqh 时间: 2009-7-24 14:28
My answer is B.

Argument : The sea turtle population would decline because of "chemical spill" 5 years ago.

Premise : More female turtles are returning to the beach for laying eggs.

Conclusion : Sea turtle population has not declined because of spill.

Weaken : We have to find a reason that the Sea turtle population is indeed facing a decline.Hence, we can weaken the Premise.

Female turtles return when they are 10 years old.So, clearly these turtles are not the ones that were affected by the spill.Maybe in another 5 years, the effect of the spill will be visible, and the number of females returning to the beach will decrease.

But now, it's just too early to make a conclusion.

Choice A cannot be right because one of the Premise already holds that "occurred...and prevented nearly all the eggs laid that year from hatching".

Hence, choice B is correct.

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