PrepTest 140, Section 3, Question 24
If the concrete is poured while the ground(44 more words not shown)
Which one of the following(15 more words not shown)
- AThe film will(46 more words not shown)
- BIf the camera(43 more words not shown)
- CThe photograph will(29 more words not shown)
- DIf the camera(43 more words not shown)
- EThe camera will(43 more words not shown)
Reading the argument
This argument works. The either-or conclusion is doing important work.
Pouring on wet ground leads to a weak foundation, and a weak foundation must either settle unevenly or crack. Now suppose the concrete settles evenly. If it was poured on wet ground, it still has to satisfy the last rule. Uneven settling is ruled out, so it must crack. If it wasn't poured on wet ground, the other option in the conclusion—dry ground—is satisfied instead.
That gives us the conclusion: with even settling, either the ground was dry or the concrete will crack. We are not concluding that dry ground guarantees a solid foundation. Dry-ground concrete could fail for another reason; the argument never excludes that.
What we’re looking for
For the parallel, track the whole sequence: one starting condition produces an intermediate condition, which produces one of two outcomes. The conclusion rules out the first outcome and says either the starting condition was absent or the second outcome occurs.
Working the answers
- ACorrect
A malfunctioning camera corresponds to wet ground. Improperly exposed film corresponds to the weak foundation. A blurred photograph corresponds to uneven settling, and a dark photograph corresponds to cracking.
A malfunctioning camera leads to improper exposure, which leads to blur or darkness. If there is no blur, then either the camera was working properly or the photograph must be dark. That matches every link and the original's either-or conclusion, even though the first sentence puts its 'if' clause at the end.
- B
A working camera prevents blur, while either bad exposure or bad development produces blur. The conclusion therefore rules out both defects when the camera works. That isn't a starting condition leading through an intermediate condition to two possible outcomes. It uses two possible causes of one outcome and concludes that both causes are absent.
- C
This starts directly with a malfunctioning camera producing blur or darkness. There is no intermediate exposure step corresponding to the weak foundation. It also states as a fact that this photograph is not blurred, then concludes that no darkness would mean the camera works. That related reasoning doesn't reproduce the full structure.
- D
Here, proper exposure or a correction during development can produce a photograph that isn't dark. The alternatives are on the condition side of the rule: either one can lead to the same result. In the original, a single intermediate condition leads to alternative results. D's conclusion also simply follows the chain to one result instead of giving the original either-or conclusion.
- E
'Only if' gives a legitimate rule: a properly working camera requires proper exposure. Too much or too little light prevents that exposure, so either lighting problem prevents the camera from working. The word 'only' doesn't make E wrong. The structure does: either of two starting problems blocks a requirement, rather than one starting condition leading through an intermediate step to two outcomes.
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