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可是俺想不通，A取非的意思就是大量的非法捕鱼导致可捕的鱼数量急剧下降，不是削弱结论而是加强结论啊。如果题目问的是“weaken”到时有可能的，但是题目问的是“assumption”。请NN们解释啊……谢谢！