求 GWD13-Q19

Sunfisher006

这道题只有两个人问，可是都没有人回答~~~ 是太简单了么？？可是我完全搞不懂这题在说什么啊  哪位NN能给我解释一下吗？这篇的逻辑是怎样的呢？

In 1992 outlaw fishing boats began illegally harvesting lobsters from the territorial waters of the country of Belukia. Soon after, the annual tonnage of lobster legally harvested in Belukian waters began declining; in 1996, despite there being no reduction in the level of legal lobster fishing activity, the local catch was 9,000 tons below pre-1992 levels. It is therefore highly likely that the outlaw fishing boats harvested about 9,000 tons of lobster illegally that year.
Which of the following is an assumption on which the argument depends?
A.    The illegal lobster harvesting was not so extensive that the population of catchable lobsters in Belukia’s territorial waters had sharply declined by 1996
B.    The average annual lobster catch, in tons, of an outlaw fishing boat is has increased steadily since 1992.
C.    Outlaw fishing boats do not, as a group, harvest more lobsters than do licensed lobster-fishing boats.
D.    The annual legal lobster harvest in Belukia in 1996 was not significantly less than 9,000 tons.
E.    A significant proportion of Belukia’s operators of licensed lobster-fishing boats were out of business between 1992 and 1996

答案是A

applemay

LS, read carefully.  The first sentence of the stimulus says:
In 1992 outlaw fishing boats BEGAN illegally harvesting lobsters from the territorial waters of the country of Belukia

Sunfisher006

对于这道我刚搜到了一个解释：
题目的大致意思是：自92年outlaw fishing boats开始非法捕虾（92年以前没有这事），随即年捕虾（合法的）总量开始下降；1996年，年捕鱼虾比92年前下降了9000吨，但捕虾活动并未减少。因此，很可能outlaw fishing boats捕了9000吨。
公式一、可捕虾总量=合法捕量(local catch)+非法捕量(illegal harvest)
公式二、96年的可捕虾总量=local catch+9000（结论中的非法捕虾量）
假设：96年以前的非法捕虾没有导致可捕虾总量急剧下降。（看公式二：如果总量急剧下降，那么在local catch不变的情况下，结论中非法捕虾量就一定小于9000，即结论不成立）
我的疑问是：原文说the local catch was 9,000 tons below pre-1992 levels，就是说1996年的合法捕捞比1992年的合法捕捞少9000吨~~~然后就得出1996年的非法捕捞是9000吨。
按照上面的公式：96年的可捕虾总量=local catch+9000（结论中的非法捕虾量）
那假设92的合法捕捞是1.2万吨，非法捕捞是2万吨，那总捕捞就是3.2万吨，然后1996年的总捕捞没有变还是3.2万吨，但是合法的少了9千吨，那非法捕捞应该是3.2万—3千=2.9万吨才对啊~~怎么会是9千吨呢？？
求解求解~~~

applemay

Necessary assumption. Use negation.

If you negate A, you have "The illegal lobster harvesting was so extensive that the population of catchable lobsters in Belukia’s territorial waters had sharply declined by 1996." If this is true, then the total avaialbe lobsters for both legal and illegal catchers are declined sharply. Therefore the 9000 ton difference between 1996 and 1992 are less likely to be caused by the illegal harvest. The conclusion does not hold. So A is the correct answer.

Sunfisher006

谢谢楼上的~~~ 但是我还有疑问：

（1）the local catch was 9,000 tons below pre-1992 levels. 这里的local catch是包括合法捕虾和非法捕虾的数量吗？

（2）It is therefore highly likely that the outlaw fishing boats harvested about 9,000 tons of lobster illegallythat year. 这里的that year 是指1992年呢 还是1996年？？

（3）选项A.  The illegal lobster harvesting was not so extensive that the population of catchable lobsters in Belukia’s territorial waters had sharply declined by 1996   这句话怎么理解呢？是说非法捕虾的数量没有大增，然后1996年大量下降？？？

kittenalways

不牛啊，这篇说的事1992开始有非法捕虾，然后合法的捕虾吨数开始下降，到1996后，合法捕虾吨数已经没有下降了，但是比1992年前的水平低9000，然后结论是非法捕虾为9000.
为什么说合法捕虾吨数少9000.然后非法捕虾数就是9000呢？作者隐含了一个前提，那就是每年的捕虾数是不变的，捕虾数要不变那么能捕到的虾就得不变，a给出了这个前提