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#23 - Zoologist: Plants preferentially absorb heavy nitrogen

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Please post below with any questions!
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This question really confused me. Can someone help me out?

I chose E on the test, but I wasn't really sure about it. Why is D right?
Emily Haney-Caron
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Hi lll7,

Here's how the argument can be summarized:
Meat eating animals have even higher nitrogen levels than herbivores
Bone samples from ice age bears have the same nitrogen levels as blood samples from today's bears
Today's bears eat meat
Therefore, ice age bears ate some meat

This only follows if the readings from bone samples and blood samples are equivalent; otherwise, we might be comparing apples to oranges! That's what D is saying.

E, on the other hand, doesn't tell us a whole lot, because we're not comparing bone to bone, we're comparing bone to blood.
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I can see why D is correct, but just want to be sure about understanding why B is wrong. Is B a "shell answer" because it tangentially addresses the concerns of D, but is ultimately irrelevant since the rate of accumulation isn't the stimulus' topic and rather accumulation generally is the focus? Thanks for your help:)
Jonathan Evans
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Good analysis. This argument itself includes a classic Shell Game™ between bone samples and blood sampled (really a primo example of Shell Gamin' if ever there were one). Answer Choice (B) is also Shell-ish—you've identified the issue; we don't care about "rate"—but sometimes these kinds of "new information" answers can be helpful in Strengthen and Weaken situations, depending on the argument. The issue here is twofold:

  1. First, (D) without a doubt most strengthens the conclusion because it makes the connection explicit between "bone samples" and "blood samples." The information in Answer Choice (B) can't hold a candle to it.
  2. Second, Answer Choice (B) actually shifts the focus to providing information about the rate of accumulation, as though we cared. The rate might be useful if it told us something about the integrity of the information about the overall levels, but this answer choice seems to be interested in rate qua rate. We certainly are not.

Thus, (B) is a two-time loser. (D) is way more on point, and (B) tries to take us down an irrelevant, primrose path to wrong answer-ville.

I hope this helps.