Complete Question Explanation
Parallel Reasoning—SN. The correct answer choice is (A)
This stimulus contains a complicated conditional argument. Undoubtedly, this question was designed to eat your time at the end of the section. Due to the complexity of the relationships involved, diagramming this question was a must.
The stimulus begins with a conditional premise, which provides that “if the concrete is poured while the ground is wet, it will not form a solid foundation.” We can diagram this statement as:
PGW = concrete poured while the ground is wet
SF = concrete will not form a solid foundation
Next, building off the term SF from the first premise, we learn that the concrete will either settle unevenly or crack if the foundation is not solid (SF).
SU = concrete will settle unevenly
C = concrete will crack
Joining the first and second premises across the common term SF produces the following diagram:
PGW SF or
While this diagram reveals a rather simple additive inference, the stimulus author opts for a more complicated ending. Invoking the contrapositive of the conditional chain, the argument concludes that “if the concrete settles evenly (SU), either it was poured while the ground was dry or it will crack.” We can diagram this relationship as:
At first glance, this may appear to be a flawed statement of the contrapositive. However, recall that the final necessary condition was an “or” compound condition. To be certain that the concrete was not poured while the ground was wet (PGW), we must be told both that the concrete settles evenly (SU) and that the concrete does not crack (C). To review, the contrapositive of the relationship provided by the first and second premises would be:
So, the conclusion does not express the contrapositive. Instead, it simply informs us that one of the two necessary conditions has not been satisfied. In that circumstance, the options are either that the sufficient condition has not been met (PGW), or it has been met (PGW) and the other necessary condition must be the case (C).
The question stem shows that this is a Parallel Reasoning question. Given the stimulus’ complicated conditional argument, we want to avoid diagramming as many of the answer choices as possible. A more efficient method is to use the Match the Conclusion test to knock out any answer choice that does not contain a sufficient condition requiring an either/or necessary condition.
Answer choice (A): This is the correct answer choice, and can be diagrammed as:
CWP = camera working properly
PE = film will be properly exposed
B = photograph will be blurred
D = photograph will be dark
As with the argument in the stimulus, the first and second premises can be joined:
CWP PE or
And, the argument concludes by stating that if one of the necessary conditions is not satisfied (B), then either the sufficient condition has not been met (CWP) or the other necessary condition will be satisfied (D):
Answer choice (B): We can quickly eliminate this answer choice using the Match the Conclusion test, because the conclusion describes a both/and necessary condition, rather than an either/or condition as in the stimulus and in answer choice (A).
Answer choice (C): As with answer choice (B), we can eliminate this choice because it does not have an either/or necessary condition in the conclusion.
Answer choice (D): Again, as with both answer choices (B) and (C), we can eliminate this answer using the Match the Conclusion test because its conclusion does not have an either/or necessary condition.
Answer choice (E): We similarly can eliminate this answer choice, because the conclusion has an either/or sufficient condition rather than an either/or necessary condition.