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  3. The binary planet hypothesis—that Earth and the Moon formed simultaneously by the accretion of smaller objects—does not explain

The binary planet hypothesis—that Earth and the Moon formed simultaneously by the accretion of smaller objects—does not explain

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问题 The binary planet hypothesis—that Earth and the Moon formed simultaneously by the accretion of smaller objects—does not explain why the Moons iron core is so small relative to the Moons total volume, compared with Earth’s core relative to Earths 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 liquefied iron core of Earth. The ejected matter—mantle rock that had surrounded the cores of both objects—would be almost devoid of iron. This matter would become the Moon.
According to the passage, the binary planet hypothesis holds that
选项 A、Earth and the Moon were formed at the same time
B、smaller objects joined together to form Earth and the Moon
C、the Moons core is the same absolute size as Earths core
答案A，B
解析 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 first 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 Earths core and the Moons core; it only compares their sizes relative to the volumes of the two objects.
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