PrepTest 104, Section 1, Question 11
A local chemical plant produces pesticides that can(36 more words not shown)
Which one of the following(15 more words not shown)
- AThe bacteria that(30 more words not shown)
- BA diet low(46 more words not shown)
- CAnimals that are(25 more words not shown)
- DApes are defined(33 more words not shown)
- EThe only animal(31 more words not shown)
Reading the argument
The timing makes the chemical plant worth investigating. It produces pesticides that can make otters sterile, and sterility rose soon after it opened. But “worth investigating” isn't “definitely contaminating the river.”
Could something else have made the otters sterile? Imagine, however unlikely, someone secretly sterilizing them. The observed increase would still happen without pesticides leaking into the water. We don't need to believe that is the actual explanation; it exposes why the stated facts don't establish the cause with certainty.
What we’re looking for
For a parallel flaw, keep the pieces straight. We know one thing can cause a particular effect. Then the effect appears after a change, and the author concludes that the possible cause must be present. We're looking for that unsupported certainty, not simply any bad argument about animals.
Working the answers
- A
The bacteria correspond roughly to a possible source of harm, but the rest doesn't match. A doesn't observe horses contracting more tetanus and infer that a possible cause is present. It starts with bacteria living in horses and predicts a higher disease rate than in other animals. That comparison would require information about susceptibility and the other animals. It isn't our move from an observed effect to a definite cause.
- BCorrect
Low calcium corresponds to pesticide exposure; reduced egg production corresponds to increased sterility. The chickens begin foraging, just as the plant begins operating, and the concerning change follows. The argument then declares the food low in calcium, treating one possible explanation as certain.
But what if cold weather or insufficient water caused the lower egg production? Those are possible alternatives to investigate, just as we could investigate another cause of the otters' sterility. “Can cause” does not establish “undeniably caused this.” B matches both the sequence and the unjustified certainty.
- C
This says undernourishment makes animals susceptible to infection, then assumes that well-fed animals cannot be similarly susceptible. They might be vulnerable for other reasons. That is a different direction of mistake: a possible source of vulnerability is absent, so vulnerability is declared absent. The original observes the harmful effect and declares a particular source present.
- D
The stated description of apes involves several characteristics, including opposable thumbs and no external tail. Finding thumbs alone doesn't establish the whole description. What about the tail and the other characteristics? This uses one required feature as though it were enough to identify an ape. It doesn't infer a particular cause from an effect that has just appeared.
- E
This gives an exclusive possible animal source—a bear—then rules out bears in the area and calls the track fake. The original never says pesticides are the only possible cause of sterility; overlooking other causes is its mistake. E's stated starting point already excludes other animal sources, so its route to the conclusion is different. We need the same reasoning error, not merely a conclusion we might also question.
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