Logical reasoning PrepTest 146 · Section 2 · Question 18

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Argument Structure

Stimulus Summary:
Based on observations of pulsar surfaces, astronomers believe pulsars are made of neutrons. However, quark-filled pulsars would have a positive charge, attracting a neutron crust, so the observations are consistent with a quark-filled pulsar.

Answer Anticipation:
Don't get lost in the physics here! At its heart, this stimulus is about two theories, and a comparison between them. While words like neutrons, quarks, and pulsars can be scary, rely on the logical features that we've seen before.

The stimulus presents two competing theories:
Neutron theory—Pulsars are made of neutronsQuark theory—Pulsars are made of a quark core with a neutron crustNote that both theories have neutrons on the outside of the pulsar—which is why the stimulus notes that both theories are consistent with the observations of pulsar surfaces.

The neutron theory is attributed to a consensus among astronomers, and the author pivots from that ("However") to the quark theory. The statement in question is part of the quark theory portion of the argument, and it's after "Because," so it's a premise for that part of the argument. That may be enough to find an answer, but there's a good chance that question #18 is going to make us be more specific than that. So before we head to the answers, let's try to anticipate how the statement in question supports the conclusion.

Here, the observations showed neutrons on the surface of pulsars, and the conclusion is that the quark theory is consistent with that. The positive charge is part of an explanation of how the quark theory could lead to neutrons being on the surface—the neutrons are attracted by that positive charge to form a shell. That's an explanation for the common element in the theories, highlighting how this quark theory could result in the same observation. Let's find an answer reflecting that!

Answer Explanation:
This answer matches our anticipation, and it's a good thing we didn't stick with anticipating just that it was a premise! Helping to explain a phenomenon is premise language, and this answer reflects the quark theory—surface neutrons despite having a quark center. If you understood that the statement in question was a premise, and also the similarities and differences between the theories, you could have ended up with this answer without understanding any physics!

Key Takeaway:
Don't get lost in the physics—you'll never need to understand science to get a question right. Here, focusing on the similarities and differences between two theories, coupled with paying attention to argument structure/the pivot keyword would get you to the correct answer.

Incorrect. The statement in question is part of the post-pivot argument supporting the quark theory, so it's not challenging that claim.

Incorrect. There's no discussion in the stimulus about controversial categorizations of astral bodies.

Incorrect. There's no indication that the positive charge of quarks is a new finding. In fact, there's no specific finding used to back up the quark theory—just an application of general physical properties.

Incorrect. The mass isn't ever called into question—just what the pulsars are made from. Since we don't know that neutrons and quarks have different masses, this answer is out of scope.