Logical Reasoning

PT8 · S4 · Q11 A distemper virus has caused

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A distemper virus has caused two-thirds of the seal population in the North Sea to die since May 1988.

Conclusion

The severe pollution of the North Sea waters must have weakened the immune system of the seals so that they could no longer withstand the virus.

Intermediate Conclusion

The explanation for the deaths cannot rest solely on the distemper virus.

Evidence

There must be a reason the normally latent virus could prevail so suddenly.

Evaluate

The argument fits the Explain Curious Fact pattern.

Curious Fact: why did a normally latent virus cause such widespread seal deaths?

Author's Explanation: The severe pollution weakened the seals' immune systems, allowing the virus to prevail.

To strengthen this explanation, we can aim to rule out alternate explanations (e.g., a new strain of the virus that the seals' immune systems had never encountered) or increase the plausibility of the Author's Explanation by providing additional evidence that pollution could indeed weaken the seals' immune systems significantly enough for the virus to cause such an outbreak.

Goal

Let’s find an answer that increases the plausibility that pollution in the North Sea contributed to the weakening of the seals' immune systems, thus enabling the virus to have such a catastrophic effect.

11.

Which one of the following, if true, most strongly supports the explanation given in the argument?

Correct
At various times during the
Why this is right
If other species such as shellfish and seabirds in the North Sea also experienced unprecedentedly steep population declines in the past ten years, it increases the plausibility that there is something in the environment affecting multiple species, supporting the idea that pollution is a contributing factor. It aligns with the argument's explanation that pollution is weakening species’ immune systems, emphasizing a broader impact of the pollution. (Definitely not an appealing answer on a first pass, but ultimately our best available)
Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.
62% picked this
By reducing pollution at its
Opposite Impact
This hurts the plausibility of the story that the North Sea's pollution was a huge contributing factor. This answer makes it sound like people have been working on keeping pollution out of there.
3% picked this
For many years, fish for
No Impact
Cool, humans eat fish? This is unrelated to the seals' immune systems or why they might succumb to the virus. (seals are mammals, not fish) If anything, the fact that humans fish in the North Sea undermines the idea that it's dangerously polluted.
3% picked this
There are two species of
No Impact
Neat, there are two species of seal. That's not dealing with an alternate explanation for why they suddenly succumbed to distemper or giving us reason to think that North Sea pollution wasn't a factor.
1% picked this
The distemper caused by the
Weakens
This weakens by offering an alternate explanation for the curious fact. If the virus was new, then the seals' immune systems being unprepared is an explanation for the virus's impact that doesn't involve pollution.
30% picked this

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