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 from 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?

1. The chemical spill five years ago occurred at a time when there were neither Merrick sea turtles nor Merrick sea turtle eggs on Baker’s Beach.
2. Female Merrick sea turtles begin returning to Baker’s Beach to lay their eggs when they are ten years old.

3. Under normal conditions, only a small proportion of hatchling female Merrick sea turtles survive in the ocean until adulthood and return to lay their eggs at Baker’s Beach.
4. 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.
5. 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.

为什么B是正确答案，原题是由于化学物质的泄漏导致egg 不能孵化，从而导致海龟的种群数量减少，如果要否定该结论，那么应当寻找能够增加种群的原因，例如D

选B的理由是，因为母海龟十岁大才回此海滩产卵，因此5年前那此污染所导致的小海龟无法孵化的影响，要再过5年才能显示出来（那个时候5年前被毁灭的小海龟才会回海滩产卵）。而现在五年的增长很可能是因为灾难发生前的5年海龟数量一直在增长。

D从理论上来说也是正确的，但它并不是最有力的对refutation的counter-argument，因为它只能部分说明5年来海龟数量增长的原因，却无法回击“原油泄漏对海龟数量没有影响”的观点

D某种程度上加强了结论

环境学家认为:很多海龟回来了，所以化学物的影响没有确定

D解释说吃蛋的鸟的数量少了，所以海龟多了。

原文说因为5年来回来产卵的母龟数量增加了，所以推出环境学家的化学事故将减少海龟数量的预测是没有根据的。

先说D。因为原文说那年几乎所有的蛋都不能孵化，所以即使鸟少了、吃的蛋少了，也不能削弱化学物的产生的减少孵化出来的龟的影响。

再说B。10年的龟才能回来产卵，说明近五年来回来产卵的母龟数量的增加与5年前的事故无关，因此产卵母龟数量的增加不能推出化学事故没有影响，断桥型削弱。