PrepTest 123

[lcid:3589] Prep Test 123 LSAT — Logical Reasoning — S2 Logical reasoning

Question prompt

A new government policy 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

65+ or chronic disease → Vaccinated against the flu Each year's vaccine will only vaccinate against the strain most likely to be most prevalent. Therefore, every year will require a vaccine for a different strain.

Answer Anticipation

The conditional rule here doesn't really play into the logic of the argument since it's not trying to apply the rule to a specific individual or a subset of the population. Instead, the conclusion is about receiving a different vaccine each year, not whether someone is going to get vaccinated.
Focusing on that aspect of the argument, let's look at what supports the conclusion that a different vaccine will be required each year. That support is that the vaccine will only vaccinate against a single strain—the strain deemed to be most prevalent. So the conclusion is about a different strain, and the premise is about how to determine which strain will be vaccinated against. In order to reach the conclusion, then, a different strain has to be selected each year as the most prevalent. If there are two years in a row with the same strain, then people wouldn't need to get the vaccine again.

Answer choices

  1. A
    The number of individuals Remaining source text redacted.
    Why choice A is not credited
    Incorrect. If the argument were about the cost, or the feasibility, of being able to vaccinate everyone in the high-risk group, then this answer choice would be relevant. However, the argument is about whether these individuals will need to get a different vaccine each year, and the total number of people getting the vaccine is out of scope of that.
  2. B
    The likelihood that a Remaining source text redacted.
    Why choice B is not credited
    Incorect. The consideration as to which strain to vaccinate against is which is the most likely, so even if there are variances as to how likely there is to be an epidemic changes, one strain would still be considered the most likely to be prevalent.
  3. C
    No vaccine for the Remaining source text redacted.
    Why choice C is not credited
    Incorrect. Even if this were true and each vaccine protects only against a single strain of the flu, if the most prevalent strain repeats, people still wouldn't need to get a second vaccination. While this answer sounds good, it doesn't guarantee the conclusion as valid, so it's wrong.
  4. D
    Each year the strain Remaining source text redacted.
    Why choice D matches the stem
    Correct. If a new strain is the one selected for the vaccine each year, then high-risk individuals will have to go back for a new vaccination each year. This answer choice deals with the jump in the conclusion—between getting vaccinated for a strain and getting vaccinated for a different strain.
  5. E
    Each year's vaccine will Remaining source text redacted.
    Why choice E is not credited
    Incorrect. Side effects are outside the scope of this argument.

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