Logical reasoning PrepTest 147 · Section 1 · Question 23

Incorrect. The stimulus still states that animals who eat meat have an "even higher" concentration of heavy nitrogen than herbivores, and the number of sources of heavy nitrogen in plants doesn't change that. Also, if anything, this answer is trying to weaken the argument by suggesting that herbivores might have higher nitrogen levels than expected based just on the levels of heavy nitrogen in rainwater.

Incorrect. The rate of accumulation is out of scope since the conclusion is just about whether the prehistoric cave bears ate meat. It's the amount that matters.

Incorrect. The number of samples would be relevant, but not that the number of samples is the same. If there's only 2 samples of each, that could be a problem for the argument.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:Relationship Ð Heavy nitrogen goes from rain to plants to herbivores to meat-eaters, getting more concentrated at each step.
Study Ð Bones samples from Ice Age bears compared to blood samples from present-day, meat-eating bears. They had the same level of heavy nitrogen.
Conclusion Ð Those Ice Age bears ate at least some meat.

Answer Anticipation:
There's a lot of confusing science going on here, but these questions never require scientific knowledge or understanding. However, they do frequently require us to take a look at the study and the sample therein, so let's start there.

Looking at this study, there's a comparison of two samples—Ice Age bear bone samples (say that several times fast!) and modern bear blood samples. That's not necessarily the right comparison/sample! It's possible that nitrogen levels differ between blood and bone. If, say, bone samples have higher nitrogen than blood samples, then the heavy nitrogen in the bone samples of the Ice Age bears would actually suggest a lower level of heavy nitrogen than the modern bears.

Since this is a major jump in the stimulus, the correct answer should address it. And since we're tasked with strengthening this argument, the correct answer should note that blood and bone heavy nitrogen levels are equivalent.

Answer Explanation:
This answer addresses the subtle switch made in the stimulus—from bone samples in prehistoric bears to blood samples in modern bears. If heavy nitrogen levels differ between blood and bone, then that comparison isn't a valid one. If they don't, as this answer suggests, then the comparison at the heart of the study is more likely to be valid, strengthening the argument.

Key Takeaway:
Don't get lost in the science! Here, there was an experiment that featured a comparison. The comparison between these samples was flawed because it went from bone to blood, and the correct answer addressed that. We know that samples and comparisons are both frequently tested on the LSAT, so we didn't need to know anything about heavy nitrogen in order to focus on the right portion of this stimulus!

Incorrect. This answer goes from bones to bones, so it doesn't address the gap in the stimulus. Since we don't know for sure the heavy nitrogen levels in the bones of any bear known to eat meat (the prehistoric ones—the ones we know the bone nitrogen levels of—aren't known to eat meat, they're concluded to eat meat), this answer doesn't necessarily apply to the stimulus.