PrepTest 121 - Section 2 - Passage 3 - Question 18

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According to the theory of gravitation, every particle of matter in the universe attracts every other particle with a force that increases as either the mass of the particles increases, or their proximity to one another increases, or both. ███████████ ██ ████████ ██ █████ ███ ██████████ ██ ██████ █████████ ███ ███ ██████ █████████ ███

Theory of gravitation · Gravity is believed to have shaped the structure of the universe

Gravity = every particle of matter attracts every other particle based on the mass of particles and how close they are to each other

Puzzling phenomenon · 90% of the universe seems to be missing

The observable mass isn't enough to explain the universe.

Cosmologists' hypothesis · Dark matter

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Elaborate on dark matter · Dark matter might be neutrinos

But, neutrinos have been assumed to have no mass. So, how could they be the dark matter that helps the universe take its shape? (Come back to this paragraph for details of exactly what neutrinos are.)

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Elaborate on dark matter · Neutrinos do have mass, so they can, in theory, be dark matter

Research shows that neutrinos can oscillate. And oscillation requires mass. (Come back to this paragraph for details of exactly what oscillation is.)

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Limits of neutrinos as dark matter · Neutrinos are at most about 20% of dark matter

There must be other particles that make up the rest of dark matter. Cosmologists still find the neutrino theory of dark matter helpful.

Passage Style

Phenomenon-hypothesis (RC)

Single position

18.

Which one of the following ███████ █████ ███████ ███ ████ ████████ ██ ███ ███ ██ ███ ██████ █████████ ███████ █████████████ ████████ ███ ████████ ████████

Question Type

Meaning in context (of word, phrase, or idea)

Structure

To understand the meaning of “cohere” at the end of P2, it will help to understand the other use of “cohere” at the end of P1. There, the author states that “dark matter” is necessary to provide enough gravity to make “the huge structures cohere.” What are the huge structures? This is a reference to the “galaxies and clusters of galaxies” that scientists think were formed by gravity. In order for gravity to form those galaxies, there needs to be enough mass; the unobservable mass is dark matter. So “cohere” at the end of P1 means something like “come together or form.” Turning to the end of P2, the author makes the point that without mass, neutrinos can’t exert gravitational force. And if matter (such as neutrinos) can’t exert gravitational force, then it can’t cause other matter to “cohere.” This use of “cohere” is the same as the earlier use of “cohere,” because the author is discussing a similar point — gravity is thought to have formed galaxies, but there needs to be enough mass in order to form those galaxies. So “cohere” at the end of P2 means something like “come together or form.”

exert gravitational force

This doesn’t make sense as a replacement, because the line already uses “such force,” which is a reference to gravitational force; the word “cohere” is supposed to be a different concept. Here’s what the end of P2 would say if (A) replaced “cohere”: “Without mass, matter cannot exert gravitational force; without such force, it cannot induce other matter to exert gravitational force.”

20%

form galactic structures

This fits the meaning of “cohere” for the reasons explained below the question stem: “Without mass, matter cannot exert gravitational force; without such force, it cannot induce other matter to form galactic structures.”

61%

oscillate into another ████ ██ ██████

This doesn’t fit, because the concept of oscillation isn’t brought up until later.

become significantly more ███████

This doesn’t fit, because “cohere” is connected to the formation of stars, galaxies, and the universe. See the explanation below the question stem for more on why. But the idea of matter getting “more massive” is different. The author never suggests that galaxies formed from some matter growing bigger or gaining more mass.

fuse to produce ███ █████████

This doesn’t fit, because “cohere” is connected to the formation of stars, galaxies, and the universe. See the explanation below the question stem for more on why. But the idea of matter fusing to form new particles is different. The author never suggests that galaxies formed when new particles were created by the fusion of other particles.

12%

PrepTest 121 - Section 2 - Passage 3 - Question 18

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