[求助]GWD6-11有个小问题

Q11:
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 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 went out of business between 1992 and 1996.
   Answer: a

有个小问题，A我觉得是没错，但是解释起来有点怪：had后是不是应该有not才能使结论成立，要是按照我的翻译，就是A选项龙虾的数量减低了，那就不合题意啊，我看了天山的讨论帖，还是没回答我这个问题，请教斑竹

题目说从92年开始有了非法捕虾，并且告诉我们合法的捕虾活动水平没有下降，因此，1996年的合法捕虾的亏空就是非法捕虾造成的

但必须有关前提，即每年都有持续稳定数量的虾供大家来捕，如果虾的总数在1992到1996的时候有下降的花，那么96年少捕的虾就不能归罪于非法捕虾，而是大自然给的少了。

A说的没错：非法捕虾没有造成可供捕获的龙虾的数码大幅下降。

如果如楼主同学所说加了not，那么意思反而不对了，请注意主句的否定。

 我是这样理解的：

 A正确，非法捕虾的渔民没有使可抓的虾的数量急剧下降，否则，如果使可抓的虾急剧下降，那么合法捕虾的活动就会减少，但是原文提到没有减少，那么应该非法渔船没有使可抓的虾急剧减少