PrepTest 125

Incorrect. This answer is the phenomenon that the argument is designed to explain, so it's background.

Incorrect. This answer is the intermediate conclusion. It supports the conclusion that this sparseness is likely the reason behind the below-average number of carnivorous mammals in Australia.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Main Point

Stimulus Summary:
Australia - Average carnivorous reptiles; below average carnivorous mammals
Explanation - Probably the sparseness of Australia
Why? - Carnivorous mammals need a lot more food than carnivorous reptiles, and so the mammals are at a disadvantage where there isn't a lot of food

Answer Anticipation:
This is absolutely one of the harder Main Point questions that has appeared on the LSAT, so it's important to work through it to be sure we understand it.

The argument starts with an observed phenomenon, and when that happens, the explanation for it is almost always the main point. There are also frequently multiple explanations, and the one(s) that the author doesn't agree with are opposing points.

After the initial phenomenon, the argument does raise an explanation for it—it is "probably a consequence of" how sparse Australia is. You may be asking yourself, "Why is that probably the explanation?" And the author answers it! The reasoning for why a certain explanation is probably correct will support that explanation, so the explanation here is a conclusion of the argument.

The reasoning behind it here, though, also has a conclusion in it ("thus"). There are two ways here to determine which is the main point and which is the intermediate conclusion.

The first is structural. Since the comparison between the food needs of the two types of animals is the reasoning behind the author's explanation for the phenomenon, that's a premise supporting the explanation. And since that reasoning directly builds to the last clause ("thus. . . "), that last clause must be supported by the preceding sentence, making it the intermediate conclusion.

The second is logical. Carnivorous mammals being at a disadvantage where there's little food explains why their relatively low numbers in Australia is probably explained by the sparseness there. An argument that used the sparseness of the ecosystem to conclude that mammals are at a disadvantage where there's relatively little food makes much less sense.
The main point, therefore, is that the relative "shortage" of carnivorous mammals in Australia is probably a result of the sparseness of the ecosystems there.

Answer Explanation:
This answer reflects the author's preferred explanation for the observed phenomenon, making it the main point of the argument.

Key Takeaway:
There are some common argument structures on the LSAT, and knowing them can be helpful in breaking down more complicated arguments. One of those types is Phenomenon/Explanation passages, where the author's preferred explanation generally serves as the main point of the argument.

Incorrect. This is the reasoning behind the author's explanation, thus making it a premise of the argument.

Incorrect. This answer is a bit of a conflation between the main point and the intermediate conclusion. You can tell that it's wrong, however, because the logical force doesn't match the conclusion ("probably" there vs. certainty in this answer).