Between 1990 and 1996, shipping traffic off the coast of Tronland increased dramatically. During the same period, the annual death...

GMAT Critical Reasoning : (CR) Questions

Source: Mock

Critical Reasoning

Weaken

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Between 1990 and 1996, shipping traffic off the coast of Tronland increased dramatically. During the same period, the annual death toll for whales in those waters nearly doubled. The bodies of most of the dead whales bore marks that could well have resulted from collision with ships. It is therefore likely that the increase in shipping traffic led to the increase in whale deaths.

Which of the following, if true, most seriously weakens the argument given?

Whales show no fear of ships and do not appear to alter course to avoid them.

Although the aerial surveys of whale movements are currently being reported to ships, no such information was available to ships prior to 1996.

The increase in shipping has been accompanied by a shift to larger vessels, which are more likely to inflict serious injury if they collide with whales.

The death toll has been particularly high among whale calves, which are typically found in shallow coastal waters where shipping traffic is heaviest.

Whales of the species most common near Tronland are so highly buoyant that after death their bodies float at the surface, where they can be struck by passing ships.

Solution

Passage Analysis:

Text from Passage	Analysis
Between 1990 and 1996, shipping traffic off the coast of Tronland increased dramatically.	What it says: Shipping traffic near Tronland went up a lot during this 6-year period What it does: Sets up the first key fact about what changed during the time period What it is: Factual observation Visualization: 1990: 100 ships per month → 1996: 300 ships per month
During the same period, the annual death toll for whales in those waters nearly doubled.	What it says: Whale deaths each year almost doubled in the same timeframe What it does: Presents a second major change that happened alongside the shipping increase What it is: Statistical observation Visualization: 1990: 50 whale deaths per year → 1996: 95 whale deaths per year
The bodies of most of the dead whales bore marks that could well have resulted from collision with ships.	What it says: Most dead whales had marks that looked like they could be from hitting ships What it does: Provides physical evidence connecting the two facts we just learned What it is: Evidence from examination Visualization: Out of 95 dead whales, about 70-75 had ship collision marks
It is therefore likely that the increase in shipping traffic led to the increase in whale deaths.	What it says: The author concludes that more ships probably caused more whale deaths What it does: Draws a causal conclusion from the three pieces of evidence presented What it is: Author's conclusion

Argument Flow:

The argument presents two parallel trends (more ships, more whale deaths), adds physical evidence (collision marks), then concludes one caused the other

Main Conclusion:

The increase in shipping traffic likely caused the increase in whale deaths

Logical Structure:

This is a correlation-to-causation argument. We have timing evidence (both increased together), physical evidence (collision marks), and the author concludes the shipping increase caused the whale death increase

Prethinking:

Question type:

Weaken - We need to find information that reduces our belief in the conclusion that increased shipping traffic led to increased whale deaths

Precision of Claims

The argument makes precise claims about timing (1990-1996), quantity (dramatic increase in shipping, nearly doubled whale deaths), and physical evidence (marks on whale bodies consistent with ship collisions)

Strategy

To weaken this causal argument, we need to find alternative explanations for the increased whale deaths or reasons why the shipping-whale death connection might not be causal. We can attack the argument by showing that something else caused the whale deaths, that the marks aren't actually from ships, or that there's a different explanation for the correlation

Answer Choices Explained

Whales show no fear of ships and do not appear to alter course to avoid them.

"Whales show no fear of ships and do not appear to alter course to avoid them." This actually strengthens the argument rather than weakens it. If whales don't avoid ships, this makes it more likely that collisions would occur, supporting the conclusion that increased shipping led to more whale deaths. This doesn't provide an alternative explanation for the deaths.

Although the aerial surveys of whale movements are currently being reported to ships, no such information was available to ships prior to 1996.

"Although the aerial surveys of whale movements are currently being reported to ships, no such information was available to ships prior to 1996." This is irrelevant to weakening the argument. The lack of whale movement information before 1996 doesn't provide an alternative explanation for why whale deaths increased or why the bodies had collision marks. If anything, this could support the argument by explaining why more collisions occurred.

The increase in shipping has been accompanied by a shift to larger vessels, which are more likely to inflict serious injury if they collide with whales.

"The increase in shipping has been accompanied by a shift to larger vessels, which are more likely to inflict serious injury if they collide with whales." This strengthens the argument by providing additional support for why shipping increases would lead to more whale deaths. Larger ships that cause more serious injuries would make the shipping-death correlation even more plausible.

The death toll has been particularly high among whale calves, which are typically found in shallow coastal waters where shipping traffic is heaviest.

"The death toll has been particularly high among whale calves, which are typically found in shallow coastal waters where shipping traffic is heaviest." This strengthens the argument by showing that deaths occur most where shipping is heaviest. This correlation supports rather than undermines the causal relationship between shipping and whale deaths.

Whales of the species most common near Tronland are so highly buoyant that after death their bodies float at the surface, where they can be struck by passing ships.

"Whales of the species most common near Tronland are so highly buoyant that after death their bodies float at the surface, where they can be struck by passing ships." This weakens the argument by providing an alternative explanation for the collision marks. Instead of ships killing whales and leaving marks, this suggests whales died from other causes first, then their floating bodies were struck by ships, creating the marks after death. This undermines the key physical evidence linking shipping to whale deaths.

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