Logical reasoning PrepTest 136 · Section 4 · Question 17

Incorrect. The argument is that Pluto isn't a planet because it was a moon. This answer gets the timing wrong, as the argument isn't about something being "simultaneously" both.

Incorrect. This answer might be necessary for the conclusion to hold, but it's not sufficient as it's too weak to necessarily apply to Pluto ("Not all").

Incorrect. Pluto was ejected from its orbit, though, so this answer doesn't apply to the situation as described in the stimulus. What would have happened in a different potential universe is usually going to be out of scope in this question type.

Incorrect. This answer is closer to a Strengthen with Necessary Assumption answer (though it's not—it goes too far in saying size is irrelevant instead of just not determinative). It definitely doesn't justify the conclusion that Pluto isn't a planet—just that it might not be.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
Pluto formed around Neptune and was ejected from orbit, so it isn't a true planet.

Answer Anticipation:
Pluto will always be a planet in our hearts.

That said, note how we stripped the opening clause out of our Summary—that "Although" tells us that the author is bringing up a few concessions/counterpoints to her own argument before delving into it, so those details are unlikely to factor into the logic of the argument.

From there, we're left with a single premise justifying the conclusion—Pluto formed around Neptune, another planet. However, there's no premise establishing that a planet can't have formed around another planet. The correct answer, therefore, will need to make that connection to justify the conclusion.

Answer Explanation:
True planet → Formed exclusively around the sun. Pluto didn't form exclusively around the sun, so this answer justifies the conclusion that it's not a true planet.

Key Takeaway:
Concessions—clauses introduced by words such as "although" and "while"—are more a part of an opposing point than they are the main argument. As such, even though the author of the argument agrees with those statements, they don't go to help prove the conclusion and thus aren't a part of the core logic of the argument.