PrepTest 143

Incorrect. This answer doesn't establish that the effect on the objects is related to its orbit, and the stimulus doesn't establish anything about the size of the planets with oval orbits.

Incorrect. This answer choice cuts against the conclusion, so we can immediately eliminate it.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
Planets generally take oval orbits, whereas our solar system generally has circular orbits. Comets in our solar system have oval orbits caused by interactions with planets, so those other planets probably have their orbits because of interactions with other planets.

Answer Anticipation:
There's a lot of astronomy in this question, but we shouldn't let ourselves get distracted by that. Instead, we should focus on the logic of the question.

The first thing to note is that this is a Strengthen question, and they frequently deal in correlation/causation flaws. This argument does have a causal conclusion (interactions with other planets threw the planets into oval orbits). However, it's based on a causal premise—the argument establishes that interactions with planets did throw comets into oval orbits. A causal conclusion can be based on a causal premise, so we don't have a correlation/causation flaw.

However, note that the argument has a big shift between the premise and conclusion! The premise is about a causal relationship that affects a comet—the conclusion is about the same causal relationship affecting a planet! That's a big jump, and the argument is assuming that comets and planets are relevantly similar so that a causal relationship holding true for one probably holds true for another. Since this argument is based on assuming two things are similar, we should look for an answer that brings up another relevant similarity in order to strengthen it.

Answer Explanation:
While this answer doesn't mention comets, it does establish a fact about these planets that makes them similar to the comets in question. We know the comets came close enough to planets to have their orbits affected by them. This answer establishes that the planets in question also have planets nearby them, thus establishing a similarity that makes a similar causal relationship possible. This doesn't do much to strengthen the argument, but it does do something, and that's enough for this question.

Key Takeaway:
First, while Strengthen questions frequently have correlation/causation flaws, don't just assume one—not even when there's a causal conclusion! Causality can be supported by causal premises, as we saw here.

Second, when an argument relies on two things being similar, you can strengthen that argument by identifying another relevant similarity between them.

Incorrect. While this answer might strengthen a conclusion about comets in other solar systems, it doesn't relate comets and planets so we're still left with the big question from the stimulus—are the orbits of planets affected in the same way as comets?

Incorrect. This answer choice provides evidence that a close encounter with another planet is unlikely to have affected the orbit since one doesn't exist in that solar system!