PrepTest 102, Section 4, Question 25
The dwarf masked owl, a rare migratory bird(77 more words not shown)
The argument depends on assuming(5 more words not shown)
- ANo birds of(12 more words not shown)
- BIf the Baja(14 more words not shown)
- COn occasion the(17 more words not shown)
- DThe dwarf masked(19 more words not shown)
- ESuitable nesting sites(12 more words not shown)
Reading the argument
The owls have lost their usual nesting place. That sounds like a serious problem, but does it mean they cannot spend the winter there at all?
At first, the argument seems straightforward: these owls nest in spiny cacti, no other suitable nesting sites exist on the peninsula, and the blight destroyed every cactus. The author concludes that without efforts to restore the cacti, the owls won't make their winter home there.
But imagine the owls arrive and discover the damage. Showing up alone wouldn't disprove the conclusion; the question is whether they could stay. Maybe an owl could remain in a makeshift spot even though that spot isn't suitable for nesting. We have been told what it needs for a suitable nest, but do we know that it needs a suitable nest to make its winter home in the region?
That is the distinction I want to press. Losing suitable nesting sites must rule out staying for the winter if this argument is going to work.
What we’re looking for
The question asks what the argument depends on assuming. Look for a requirement the author needs to connect those two things. If the owls can winter there without suitable nesting sites, the missing cacti no longer establish the conclusion.
Working the answers
- A
Other birds could use these cacti too. That wouldn't change whether the dwarf masked owl needs a suitable nesting site to winter on the peninsula. The argument doesn't depend on giving this owl exclusive use of the cactus.
- B
Having cacti doesn't have to guarantee that the owls come. The author is arguing that losing the cacti keeps the owls away, not that providing cacti is enough to bring them. Perhaps a region has plenty of cacti but lacks food. B makes a stronger claim about what the presence of cacti ensures, which the argument doesn't need.
- C
We don't need to know that these owls have previously wintered far from their normal route. The conclusion says where they will not winter this time; it doesn't tell us where they will go instead or how far away that will be. A history of traveling to unusual places isn't required to infer that this particular place won't serve as their winter home.
- D
Read the direction carefully: this says that if the owls don't make their winter home on the peninsula, the region must lack spiny cacti. In other words, they couldn't stay away while cacti were present.
But they could stay away for another reason, such as unsuitable temperatures or a shortage of prey, even with plenty of cacti. The argument only needs the absence of suitable nesting sites to keep the owls away. It doesn't need that absence to be required every time the owls stay away.
- ECorrect
This supplies the connection we were looking for: wherever these owls make their winter home, suitable nesting sites must be available. The peninsula has lost its only suitable sites, so the owls cannot make their winter home there under that requirement.
Now try removing the requirement. If an owl can winter in an area without a suitable nesting site, perhaps by staying in a makeshift spot where it cannot nest, the author's evidence no longer rules out its staying on the peninsula. E closes that exact gap.
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