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#5 - Landscape architect: If the screen between these two

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Complete Question Explanation

Parallel Reasoning. The correct answer choice is (D)

This stimulus provides a landscape architect’s conditional reasoning regarding a screen: If the screen is a hedge, then that hedge must be made of either hemlocks or Leyland cypress trees:

    ..... ..... ..... ..... ..... ..... hemlocks
    Screen is hedge ..... :arrow: ..... ..... or
    ..... ..... ..... ..... ..... Leyland cypress trees

Location, however, precludes the use of Leyland cypress trees. Therefore, since the use of Leyland trees has been ruled out, if the screen must be a hedge, it must be hemlocks:

    Screen is hedge ..... :arrow: ..... hemlocks

The question stem asks which pattern of reasoning in the answer choices is most similar to that in the stimulus. In this case, the author presents a conditional statement that allows for two possibilities, and then rules out one of the two. When the second necessary condition is ruled out, it can be concluded that when the sufficient condition is present, the necessary condition that has not been ruled out must also take place.

Answer choice (A): This answer choice presents a conditional statement, and then rules out the sole necessary variable, allowing the author to draw a valid conclusion based on the contrapositive of the conditional statement:

    North side entrance ..... :arrow: ..... ramp

    Ramp ..... :arrow: ..... north side entrance

Since this choice does not involve two alternative necessary conditions, it does not parallel the reasoning in the stimulus, and this answer choice should be eliminated.

Answer choice (B): In this answer choice, the sole necessary condition is ruled out, and a new outcome is introduced:

    Visitors allowed ..... :arrow: ..... parking needed

    Parking ..... :arrow: ..... design change

This answer choice does not parallel the reasoning found in the stimulus.

Answer choice (C): Here there are two alternatives. In this scenario, however, the two alternatives are mutually exclusive—clay must exclude shale and vice versa:

    Clay ..... :arrow: ..... Shale

    Shale ..... :arrow: ..... Clay

It is then concluded, based on a test sample of shale, that the entire subsoil is made of shale (that is, there is no clay). In the stimulus, on the other hand, the “impossibility” is caused by another factor. Both Leyland cypress trees and hemlocks are legitimate choices for the hedge; only the location renders the use of Leyland cypress trees an impossibility.

Answer choice (D): This is the correct answer choice. Here, there are two alternatives for the necessary condition:
    ..... ..... ..... concrete
    path ..... :arrow: ..... or
    ..... ..... ..... stone

It is then stated that the concrete path is an impossibility. Therefore, if there is to be a path, it will have to be stone:

    path ..... :arrow: ..... stone

Thus, the necessary condition, like that in the stimulus, is left as the lone remaining alternative. The pattern of reasoning in this answer choice perfectly mirrors that found in the stimulus.

Answer choice (E): In this answer choice, there are two viable alternatives:


    ..... ..... ..... ..... ..... ..... ..... ..... potentially playground
    space the size of this meadow ..... :arrow: ..... ..... or
    ..... ..... ..... ..... ..... ..... ..... ..... picnic area


The author then points out that the picnic area would create litter and the playground would be noisy, so it is best that the space remain a meadow:

Playground and picnic area ..... :arrow: ..... remain meadow

Since both necessary variables are ruled out in this case, this pattern of reasoning does not parallel that found in the stimulus.