PrepTest 159 - Section 2 - Passage 3 - Question 15

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Since 1929, cosmologists have known that the universe is expanding. █████ █████████ ████ ███████ ████ ███ █████████ ██ ███████ ██ ███ ██████████ ███ ███████ ████ ███████ ███ ██ ███ ████ ██████ ███████████ ███ ███ ██ ███████ ███ ███████ ██ █████████ ███ █████████ ██ █████████ █████ █████ ██ ███████████ ██ █████ █████████ ███ ████████ ██████████ ████ ████ ████ ███████ ████ █████████ █████ ████████ █████ ████ ███ █████████ ██ ███ ████████ ██ ████████ █████████████

Unexpected phenomenon · Expansion of universe is accelerating, rather than slowing down

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Two potential explanations · Both challenge current understanding of the universe

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Explanation 1 · Dark energy

The idea of energy stretching space dates back to Einstein. There’s some support for this theory.

Potential origin of dark energy · Created by “virtual” particles

The particles pop in and out of existence, creating “vacuum” energy.

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Inconsistent evidence · “Vacuum” energy theory of dark energy not supported

Explanation 2 · Gravity doesn’t work as predicted across large distances

Additional details about Explanation 2 · Theory is radical and might be easier to test than dark energy theory

Passage Style

Phenomenon-hypothesis (RC)

15.

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

Question Type

Main point

For a Phenomenon-Hypothesis passage, the main point is typically that there's a hypothesis (or hypotheses) presented to explain the phenomenon. The main point should capture the author's opinion about the hypotheses, if any. Here, the author tells us about two hypotheses to explain the accelerating expansion of the universe. She doesn't support or reject either of the explanations, but does note that one might be easier to test than the other.

Researchers hypothesize the █████████ ██ ████ ██████ ██ ███████ ███ ██████████ ███████████ █████████ ██ ███ █████████

This is too narrow to be the main point of the passage, because it leaves out the second explanation.

Though there is ████ █████████████ ████████ ███ ███ ███████████ █████████ ██ ███ █████████ █████ ██ ████ ███ ██████ ████████ ███ ████ ██████ ███████

This is too narrow to be the main point of the passage, because it leaves out the second explanation. In addition, the author never suggests that there's little evidence of dark energy. There may be little evidence of "vacuum" energy as the origin of dark energy, but this doesn't imply that there's little evidence of dark energy.

The current proposals █████ ███ ██████ ██ ████ ██████ ██████ ████ ██████████ ███████ ██████ ██ ██████████ ██ ██████████ ██ ██████ ██ ████ ███████

This isn't supported, so it can't be the main point. The second theory suggests Einstein's theory of relativity is flawed or incomplete. But we're not told the first theory (dark energy) calls Einstein's theory into question. The first theory may call into question our current conception of the universe, but this isn't the same as calling Einstein's theory of relativity into question. In any case, the main point isn't about the consequences of the two explanations on Einstein's theory; it's that cosmologists have presented the two explanations for the accelerated expansion of the universe.

Scientists have proposed ███ ████████████ ██ ███ ███████████ █████████ ██ ███ █████████ ███ ███████ ████ █████████ ████ ████████ ████████

This best captures the main point. It's the only answer choice that (1) doesn't say anything unsupported and (2) captures both of the explanations discussed for the accelerated expansion of the universe.

82%

The best explanation ██ ███ ███████████ █████████ ██ ███ ████████ ██ ███ ████ ███████ ███ ██████ ██ ████ ███████

This isn't supported, so it can't be the main point. Although the author notes that the second theory may be easier to test than the dark energy theory, this doesn't imply that the author thinks dark energy theory is wrong.

PrepTest 159 - Section 2 - Passage 3 - Question 15

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