PrepTest 156

[lcid:3721] Prep Test 156 LSAT — Logical Reasoning — S2 Logical reasoning

Question prompt

Body temperature can be Remaining source text redacted.
Why the credited answer is right

Credited answer: B

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Argument

Valid or Flawed

Flawed

Strategy Overview

Argument or facts? Always argument, so identify premises and conclusions of argument Anticipate why the premises are not enough to show that the conclusion is true
Causal argument? Look for answer choice that:
Shows possible alternate cause Shows cause without effect Shows effect without cause Shows the cause and effect are reversed
If not causal argument, anticipate ways to worsen problem with argument
Use anticipations to select the answer choice that, if true, would weaken argument

Answer Anticipation

Our ultimate goal is to find the answer choice that weakens the argument. However, it's much easier to do that if we first break down the argument and identify its flaws. Then, weakening the argument is only a matter of finding the answer choice that exploits that flaw. Causation flaws are the most common issue on these questions, so experienced test-takers look for that flaw first. No statements in this argument are causal, so this argument doesn't commit a causation flaw. However, after breaking down this argument, an experienced test-taker would probably notice a change in the time period discussed in the premises and conclusion. The premises tells us what's true of cold-blooded animals today. However, dinosaurs lived a very long time ago. Are we sure that the temperature of a cold-blooded animal's limbs was much lower than that of the rest of its body when dinosaurs ruled the world? If so, then we have pretty good evidence that dinosaurs probably weren't cold-blooded. If not, then we really can't say whether dinosaurs were cold- or warm-blooded. Experienced test-takers might identify a related problem — dinosaurs have been dead for a very long time. We're relying on "estimates derived from dinosaur fossils," which have been buried in the earth for millions of years. Are we sure these fossils accurately reflect the proportions of two oxygen isotopes in dinosaurs' bones when the dinosaurs were alive? Or could the proportion of these isotopes have changed over millions of years? If so, these fossils aren't reliable evidence of dinosaurs' warm- or cold-bloodedness. So, the correct answer will probably weaken the argument by exploiting these problems. The correct answer may say that during the dinosaur era, cold-blooded animals' limb-to-core-body-temp ratio was similar to the ratio found in the dinosaur fossils. Or, it could say that the proportion of the oxygen isotopes in dinosaur bones can change over the millions of years they've been fossilized. Let's look for something similar to those anticipations.

Answer choices

  1. A
    Large warm-blooded animals keep Remaining source text redacted.
    Why choice A is not credited

    This doesn't weaken the argument. Still, this answer choice is a little tempting, as it suggests that large warm-blooded animals may not have a similar limb-to-core-body-temp ratio as the dinosaurs. However, we need to remember that the premises say that "dinosaurs had nearly the same body temperature in their limbs as in the rest of their bodies." The dinosaurs didn't necessarily have the exact same temperature in their limbs and the rest of their bodies. So, the evidence that large warm-blooded animals keep their "core body temperature slightly higher than the body temperature in their limbs" might be consistent with the premise about dinosaurs. Perhaps most dinosaurs also kept their core body temps slightly higher than their limb temps.

  2. B
    The fossilization process introduces Remaining source text redacted.
    Why choice B matches the stem

    As we anticipated, this answer choice weakens the argument by showing that the dinosaur fossils are not reliable evidence of the temperature of dinosaurs' limbs or bodies. If the fossilization process alters the "original oxygen isotope ratios" in unpredictable ways, we really can't use those fossils to estimate the proportions of two oxygen isotopes. And if we can't estimate that proportion, we can't say that dinosaurs' limb-to-core-body-temp ratio is similar to that of warm-blooded animals. So, by undermining the author's key piece of evidence, this answer choice weakens the argument. And because this weakens the argument in a way that conforms to our anticipation, we can select it and give the remaining answers choices an, at most, quick check

  3. C
    Oxygen was more abundant Remaining source text redacted.
    Why choice C is not credited

    This doesn't weaken the argument. We don't know whether oxygen being "more abundant in Earth's atmosphere" during the dinos' era would affect the proportion of the two oxygen isotopes in the dinosaurs' bones. Perhaps it did, but that's a major assumption we'd have to make to justify (C). Since we can't explain how (C) would weaken the argument without making this unjustified assumption, we need to eliminate it.

  4. D
    Small warm-blooded animals like Remaining source text redacted.
    Why choice D is not credited

    This answer choice doesn't weaken the argument. Still, it's a little tempting, as it tries to get us to think that large warm-blooded animals have a much different limb-to-core-body-temp ratio than dinosaurs. However, just because large warm-blooded animals have less uniform body temperatures than small warm-blooded animals doesn't mean that the temperatures of large warm-blooded animals' limbs are much lower than the rest of these animals' bodies. The temp of these animals' limbs could be only slightly lower than the rest of their bodies. And that's not necessarily inconsistent with the limb-to-core-body-temp ratio of dinosaurs, who had limbs that were "slightly" less warm than the rest of the bodies.

  5. E
    Warm-blooded animals are more Remaining source text redacted.
    Why choice E is not credited

    This doesn't weaken the argument. We don't care about how much oxygen warm-blooded animals use. We just care about the ratio of the oxygen isotopes in their bone. So, this answer choice is irrelevant to the argument.

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