PrepTest 113

[lcid:3550] Prep Test 113 LSAT — Logical Reasoning — S3 Logical reasoning

Question prompt

For the last three Remaining source text redacted.
Why the credited answer is right

Credited answer: D

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

Argument or Facts

Argument

Valid or Flawed

Flawed

Question Type

Strengthen with Necessary Premise Questions

Stimulus Summary

Problem - A certain whitefly has been ruining crops
Solution - Look for a parasite that will kill it
Approach to search - Since the whitefly was believed to be a sweet-potato whitefly, look at parasites for them
Issue - The whitefly isn’t a sweet-potato whitefly - it’s a silverleaf whitefly
Conclusion - The search has been a waste!

Answer Anticipation

The argument here is built off of a problem/solution pattern. And, as with many arguments that fall into this pattern, the author brings up an issue with the proposed solution - or, more specifically, with the approach that scientists have used to find a solution.
The goal here is to find a parasite for a certain whitefly that’s ruining crops. The search up until now has focused on sweet-potato whitefly parasites, since it was believed the new whitefly fell into this category. However, the noted issue with the approach being taken is that this whitefly isn’t a sweet-potato whitefly - it’s a different type (silverleaf).
From this, the argument draws a very strong conclusion - the search so far has been a “waste[].” That implies that sweet-potato whitefly parasites have no chance at also being a parasite to the silverleaf whiteflies. Let’s find an answer making that connection.

Answer choices

  1. A
    All varieties of the Remaining source text redacted.
    Why choice A is not credited
    Since the whitefly in question isn’t a sweet-potato whitefly, this answer doesn’t really address the situation at hand. And even if some sweet-potato whiteflies aren’t pests, finding a parasite that controls them could still be helpful in controlling this whitefly.
  2. B
    If a crop pest Remaining source text redacted.
    Why choice B is not credited
    The conclusion is about whether a search for a sweet-potato whitefly parasite was a waste of time, not whether finding such a parasite (or finding a silverleaf whitefly parasite) will guarantee successful control of the species, so this answer is out of scope.
  3. C
    The chances of successfully Remaining source text redacted.
    Why choice C is not credited
    The argument doesn’t look to future success; it just discusses whether the effort so far has been wasted.
  4. D
    No parasite of the Remaining source text redacted.
    Why choice D matches the stem
    This answer draws the connection between the work that has been done and the revelation that it was based on a faulty assumption. That faulty assumption didn’t guarantee that the effort so far had been wasted, but if it’s true that the sweet-potato whiteflies don’t share parasites with the silverleaf whiteflies, then it likely was wasted effort. If they do share parasites in common (the negation of this answer), then the effort may not have been wasted - killing this argument.
  5. E
    In the last three Remaining source text redacted.
    Why choice E is not credited
    First, the argument suggests that this answer isn’t even true, as it states that the scientists have confined their search to parasites of the sweet-potato whitefly - suggesting that some exist and they’ve been considering them as potential solutions here. But assuming that that’s not the case, this answer still isn’t necessary. The entomologists may have found some such parasites, they just didn’t affect the whitefly in question since it was actually a silverleaf whitefly.

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