Logical reasoning PrepTest 135 · Section 1 · Question 13

Question prompt

Researchers have studied the Remaining source text redacted.
Why the credited answer is right

Credited answer: E

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 Questions

Stimulus Summary

Salt-water plants require more water, but can use seawater, which is much cheaper to pump at sea level than regular water. So seawater agriculture should be cost-effective in deserts near sea level, despite smaller yields.

Answer Anticipation

The argument is all about the cost-effectiveness of seawater agriculture in areas near the sea that lack other sources of water (i.e., deserts). What’s the cost-effectiveness based on? Not yields - the conclusion notes that yields are smaller. No, the argument relies on another cost being cheaper - the pumping of seawater instead of freshwater.
Whenever the conclusion of an argument makes a call about the net benefit of something, or it concludes that one option is “better” than another, it has to establish the relevant criteria. Here, the argument never establishes what the largest costs associated with agriculture are.
Since the argument relies on the pumping costs being cheaper as supporting a conclusion that, overall, salt-water agriculture will be cost-effective, it has to be established that this cost is a driving cost towards the net amount. If pumping costs are insignificant overall, then the argument is a poor one. If, however, they’re a large proportion of the total cost, then it’s better. So let’s find an answer establishing that these costs are significant.

Answer choices

  1. A
    A given volume of Remaining source text redacted.
    Why choice A is not credited
    Without knowing if these plants are more nutritious, less nutritious, or as nutritious but with different nutrients, it’s impossible to know how this answer affects the argument. Be wary of these answers with “neutral” language in Strengthen and Weaken questions!
  2. B
    Some halophytes not only Remaining source text redacted.
    Why choice B is not credited
    If anything, this answer cuts against the argument by creating a restriction on halophytes that wasn’t present in the stimulus (they “require” salt water), thus limiting their use.
  3. C
    Large research expenditures are Remaining source text redacted.
    Why choice C is not credited
    If anything, this brings up a significant cost of implementing halophytes, calling into question whether they would be cost-effective to use.
  4. D
    Costs other than the Remaining source text redacted.
    Why choice D is not credited
    Similar to (A), this answer doesn’t state whether these different costs are higher or lower, so it’s impossible to know what effect this has on the argument.
  5. E
    Pumping water for irrigation Remaining source text redacted.
    Why choice E matches the stem
    If pumping water is one of the driving factors in cost-effectiveness, then the fact that it’s much cheaper to do so with sea water at sea level than from deep wells suggests that the costs will be lower for this type of agriculture, backing up the conclusion.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 5%
  2. B 6%
  3. C 1%
  4. D 7%
  5. E Credited 81%

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