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Complete Question Explanation

Justify the Conclusion—SN. The correct answer choice is (A)

The argument involves the use of conditional reasoning. Note the use of the word “unless” in the first sentence. The first sentence can be diagrammed using the Unless Equation, and the remainder of the argument has the following structure:
  • ..... ..... ..... ..... ..... ..... ..... ..... ..... ..... ..... Permit obtained by Feb. 1

    Premise (1): ..... Library completed on schedule ..... :arrow: ..... or

    ..... ..... ..... ..... ..... ..... ..... ..... ..... ..... ..... Some activities completed in less time


    Premise (2): ..... Permit obtained by Feb. 1


    Conclusion: ..... Library completed on schedule
The contrapositive of the first premise guarantees that this conclusion would follow if the building permit cannot be obtained by February 1 and none of the other necessary activities can be completed in less time than originally planned:

  • ..... ..... Permit obtained by Feb. 1

    Premise (1): ..... ..... + ..... ..... ..... ..... :arrow: ..... ..... Library completed on schedule

    ..... ..... Some activities completed in less time
The stimulus states that the first of these two conditions has been met. Therefore, any answer choice that clearly shows the second condition has been met (i.e. that none of these activities will be completed in less time than originally planned) would justify the argument’s conclusion. Note that the logical opposite of “some” is “none.”

Answer Choice (A): This is the correct answer choice. If all of the other activities necessary for construction take at least as much time as originally planned, then we know that none of these activities will be completed in less time than originally planned. If this is true, then both conditions have been met that guarantee the new library will not be completed on schedule.

Answer Choice (B): This admission by the officials does not guarantee that the library will not be completed on schedule. The officials admit that the library probably will not be completed on schedule, which still leaves open the possibility that it could be completed on schedule.

Answer Choice (C): This answer choice does not help the argument, let alone prove the conclusion. We already know from the premises that the building permit will not be obtained by February 1, so this answer choice does not add any relevant information to the argument.
Answer Choice (D): Once again, this answer choice is not helpful. While this may explain why the building permit will not be obtained by February 1, it does not prove that the library will not be completed on time.

Answer Choice (E): This answer choice makes it more likely that the building will not be completed on time, but it does not quite prove it. Many tempting incorrect answer choices on Justify the Conclusion questions are helpful facts that help strengthen the argument. But in order to be correct on a Justify the Conclusion question, the answer choice must prove the author’s conclusion definitively.

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