LSAT Explanation PT 25, S4, Q25: The dwarf masked owl, a rare

LSAT Question Stem

The argument depends on assuming which one of the following? 

Logical Reasoning Question Type

This is a Necessary Assumption question. 

Correct Answer

The correct answer to this question is E. 

LSAT Question Complete Explanation

Let's first analyze the argument in the passage. The passage discusses the dwarf masked owl, which normally makes its winter home on the Baja peninsula, nesting in spiny cacti. The passage states that there are no other suitable nesting sites for the owl on the Baja peninsula. However, a blight destroyed all the spiny cacti on the Baja peninsula last spring. The conclusion of the argument is that unless steps are taken to reestablish the spiny cactus population, the dwarf masked owl will not make its home on the Baja peninsula this winter.

The structure of the argument can be broken down as follows:

1. Premise: The dwarf masked owl nests in spiny cacti on the Baja peninsula.

2. Premise: There are no other suitable nesting sites for the dwarf masked owl on the Baja peninsula.

3. Premise: A blight destroyed all the spiny cacti on the Baja peninsula.

4. Conclusion: Unless steps are taken to reestablish the spiny cactus population, the dwarf masked owl will not make its home on the Baja peninsula this winter.

An "Evaluate" question for this argument could be: "Are suitable nesting sites a requirement for the dwarf masked owl to make its winter home on the Baja peninsula?"

The question type for this problem is Necessary Assumption, which asks us to identify the assumption on which the argument depends. The correct answer is E.

Now let's discuss each answer choice:

a) No birds of prey other than the dwarf masked owl nest in the spiny cactus.

- This answer choice is irrelevant to the argument because it focuses on other birds of prey, which are not the focus of the argument. The argument is concerned with the dwarf masked owl and its nesting sites.

b) If the Baja peninsula contains spiny cacti, then the dwarf masked owl makes its winter home there.

- This answer choice reverses the logic of the argument. The argument states that the owl needs spiny cacti to nest, but it doesn't necessarily mean that the presence of spiny cacti guarantees the owl will make its winter home there.

c) On occasion the dwarf masked owl has been known to make its winter home far from its normal migratory route.

- This answer choice brings up an irrelevant piece of information. The argument is focused on the Baja peninsula and the necessity of spiny cacti for nesting, not the owl's migratory route.

d) The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti.

- This answer choice is a mistaken reversal of the connection in the argument. The argument states that the owl needs spiny cacti to nest, but this answer choice suggests that the absence of spiny cacti is the only condition under which the owl won't make its winter home on the Baja peninsula.

e) Suitable nesting sites must be present where the dwarf masked owl makes its winter home.

- This is the correct answer because it connects the premises and the conclusion. It links the concept of "no suitable nesting sites" from the premises to the concept of "not make their home there" in the conclusion. It assumes that the owl will only make its winter home in a location with suitable nesting sites, which is crucial to the argument.

In summary, the correct answer is E because it connects the premises and the conclusion, filling the gap between the concepts of "nesting sites" and "winter home." The other answer choices are either irrelevant, mistaken reversals, or focus on information not central to the argument.