LSAT Explanation PT 24, S2, Q3: A group of unusual meteorites was

LSAT Question Stem

The argument derives its conclusion by 

Logical Reasoning Question Type

This is a Method of Reasoning question. 

Correct Answer

The correct answer to this question is B. 

LSAT Question Complete Explanation

Let's first break down and analyze the argument in the passage. The passage discusses a group of unusual meteorites found in Shergotty, India. The structure of these meteorites indicates that they originated from one of the geologically active planets: Mercury, Venus, or Mars. The passage then explains why Mercury and Venus cannot be the source of these meteorites, leading to the conclusion that they probably came from Mars.

Here's the structure of the argument:

1. Premise: The meteorites' structure indicates they originated from Mercury, Venus, or Mars.

2. Premise: Material dislodged from Mercury would be captured by the Sun, not falling to Earth as meteorites.

3. Premise: Venus' gravity would prevent dislodged material from escaping into space.

4. Conclusion: The meteorites probably fell to Earth after being dislodged from Mars.

Now, let's identify the question type and what it's asking us to do. This is a Method of Reasoning (MOR) question, which asks us to determine how the argument derives its conclusion. In this case, we need to identify the method used to reach the conclusion that the meteorites probably came from Mars.

Let's analyze each answer choice:

a) Offering a counterexample to a theory

While the passage does mention other planets (Mercury and Venus) and explains why they cannot be the source of the meteorites, it does not offer a counterexample to a specific theory. Instead, it eliminates these planets as possible sources. So, this answer choice is incorrect.

b) Eliminating competing alternative explanations

This answer choice is correct. The passage eliminates Mercury and Venus as possible sources for the meteorites by explaining why material from these planets would not end up on Earth. After eliminating these alternatives, the argument concludes that the meteorites likely came from Mars.

c) Contrasting present circumstances with past circumstances

The passage does not compare present and past circumstances. It focuses on explaining the possible origins of the meteorites and eliminating alternative explanations. This answer choice is not relevant to the argument's method of reasoning, so it is incorrect.

d) Questioning an assumption

The passage does not question any assumptions. Instead, it provides reasons for eliminating Mercury and Venus as possible sources of the meteorites, leading to the conclusion that they probably came from Mars. This answer choice is incorrect.

e) Abstracting a general principle from specific data

The passage does not derive a general principle from specific data. It focuses on the origins of a particular group of meteorites and provides reasons for eliminating alternative explanations. This answer choice is not relevant to the argument's method of reasoning, so it is incorrect.

In summary, the correct answer is B, as the argument derives its conclusion by eliminating competing alternative explanations (Mercury and Venus) and concluding that the meteorites probably came from Mars.