GMAT question Pack 1 CR

richachampion wrote: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.

Premise: 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.
Conclusion: It is therefore highly likely that the outlaw fishing boats harvested about 9,000 tons of lobster illegally that year.

The argument assumes that the portion in red is the ONLY POSSIBLE EXPLANATION for the 9000-ton deficit in the 1996 local catch.

Apply the NEGATION TEST.
When the correct answer choice is negated, the conclusion will be invalidated.

A, negated:
The illegal lobster harvesting was so extensive that the population of catchable lobsters in Belukia's territorial waters had sharply declined by 1996.
This negation offers an ALTERNATE explanation for the 9000-ton deficit in the 1996 local catch -- a decline in the lobster population, as indicated by the portion in blue -- invalidating the conclusion that outlaw boats in 1996 were responsible for the deficit.
Since the negation of A invalidates the conclusion, A is an assumption: a statement that MUST BE TRUE for the conclusion to hold.

The correct answer is A.

E, negated:
A significant proportion of Belukia's operators of licensed lobster-fishing boats went still in business between 1992 and 1996.
This negation seems to confirms the premise that there was no reduction in the level of legal lobster fishing activity.
But it is still entirely possible that outlaw boats in 1996 were responsible for the 9000-ton deficit in the local catch.
Since the negation of E does not invalidate the conclusion, eliminate E.

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