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The binary planet hypothesisthat Earth and the Moon formed simultaneo

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Question 1

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A,B

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The binary planet hypothesis—that Earth and the Moon formed simultaneously by the accretion of smaller objects—does not explain why the Moon’s iron core is so small relative to the Moon’s total volume, compared with Earth’s core relative to Earth’s total volume. According to the giant-impact hypothesis, the Moon was created during a collision between Earth and a large object about the size of Mars. Computer simulations of this impact show that both of the objects would melt in the impact and the dense core of the impactor would fall as molten rock into the liquefed iron core of Earth. Te ejected matter—mantle rock that had surrounded the cores of both objects—would be almost devoid of iron. Tis matter would become the Moon.

For the following question, consider each of the choices separately and select all that apply.

1. According to the passage, the binary planet hypothesis holds that

A. Earth and the Moon were formed at the same time
B. smaller objects joined together to form Earth and the Moon
C. the Moon’s core is the same absolute size as Earth’s core

2. The giant-impact hypothesis as described in the passage answers all of the following questions EXCEPT:

A. What happened to the rock that surrounded the impactor’s core afer the impactor hit Earth?
B. What happened to the impactor’s core afer the impactor hit Earth?
C. Where did the impactor that collided with Earth originate?
D. Why is the Moon’s iron core small relative to that of Earth?
E. What was the size of the impactor relative to that of Mars?

3. Which of the following best describes the organization of the passage?

A. The development of one theory into another is outlined.
B. Two explanations are provided, both of which are revealed as inadequate.
C. A theory is presented, and then evidence that undermines that theory is discussed.
D. Similarities and differences between two theories are described.
E. A flawed hypothesis is introduced, and then an alternative hypothesis is presented.

Show Answer Question #1

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A,B

Show Answer Question #2

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Show Answer Question #3

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The passage discusses two hypotheses about the formation of Earth’s moon and explains why one of them appears to be more plausible than the other.

OE

1. According to the passage, the binary planet hypothesis holds that

Choices A and B are correct. The question asks what the binary planet hypothesis holds.

Choice A is correct: According to the first sentence of the passage, the binary planet hypothesis holds that “Earth and the Moon formed simultaneously,” that is, at the same time.

Choice B is correct: According to the frst sentence of the passage, the binary planet hypothesis holds that Earth and the Moon formed “by the accretion of smaller objects,” that is, by smaller objects joining together.

Choice C is incorrect: The passage does not mention the absolute sizes of Earth’s core and the Moon’s core; it only compares their sizes relative to the volumes of the two objects.

Answer: A,B

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OE

2. The giant-impact hypothesis as described in the passage answers all of the following questions EXCEPT:

The questions in Choices A, B, D, and E are all answered by the giant-impact hypothesis: for Choice A, the rock that surrounded the impactor’s core “would become the Moon”; for Choice B, the impactor’s core “would fall as molten rock into the liquefed iron core of the Earth”; for Choice D, the Moon’s iron core is small relative to the Earth’s core because the matter that formed the Moon was “almost devoid of iron”; and for Choice E, the passage states that the impactor was “a large object about the size of Mars.” But nothing in the passage refers to the origin of the impactor, so Choice C is the correct answer.

Answer: C

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OE

3. Which of the following best describes the organization of the passage?

The passage begins by presenting the binary planet hypothesis about the formation of Earth and the Moon and claiming that the hypothesis fails to explain the disparity in the sizes of Earth’s iron core and the Moon’s iron core relative to their volumes. The passage then introduces an alternative—the giant-impact hypothesis—and argues that this alternative explains the disparity better. Thus, Choice E is correct.

The second theory is not presented as having been developed out of the frst, so Choice A is incorrect; only the frst theory is revealed as inadequate, so Choice B is incorrect; and the two theories are not compared extensively, so Choice D is incorrect. Although “a theory the binary planet hypothesis] is presented, and then evidence that undermines that theory [the disparity related to iron cores] is discussed,” that description fails to capture the organization of the passage as a whole, so Choice C is incorrect.

Answer: E