TPO74阅读真题+题目+答案下载：Lunar History

TPO74阅读真题+题目+答案下载：Lunar History

Much is still unknown about the Moon's origin.Until recently,the most widely held hypothesis argued that the formation of the Moon paralleled that of Earth and the other planets.That is,the Moon formed from minute rock fragments and gases that composed a disk-shaped structure (the solar nebula)that orbited the early Sun. Debris from this disk collided and accumulated into larger masses that,in turn, accreted into planetary-sized bodies.

A new hypothesis,which has recently gained support from many scientists, suggests that a giant body collided with Earth to produce the Moon.The explosion caused by the impact of a Mars-sized body with a semi-molten Earth is thought to have ejected huge quantities of mantle rock from the primordial Earth.A portion of this ejected material remained in orbit around Earth,while the remainder either escaped or impacted upon Earth's surface.In a manner similar to that proposed in the earlier hypothesis,the material orbiting Earth then began to accumulate, eventually producing the Moon.Though the giant impact hypothesis provides a plausible mechanism for the Moon's formation,many questions must be answered before this proposal can be considered viable.

Despite the fact that the origin of the Moon is still debated,planetary geologists have been able to work out some of the basic details of the Moon's history,using among other things variations in crater density (quantity per unit area).Simply stated,the higher the crater density,the longer the topographic feature has existed. During its early history,the Moon was continually impacted as it swept up debris from the solar nebula.This continuous bombardment and perhaps radioactive decay generated enough heat to melt the Moon's outer shell and quite possibly the rest of the Moon as well.

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托福TPO74阅读题目：

1.The word "minute" in the passage is closest in meaning to 

A tiny 

B numerous 

C Heavy 

D precious

2.Paragraph 1 supports which of the following statements about the origins of Earth? 

A Earth formed from debris surrounding the Sun. 

B Earth was disk-shaped in the earliest stage of its formation. 

C Earth formed from a large mass that did not collide with debris. 

D Earth formed after the Moon had already been formed.

3.According to the new hypothesis described in paragraph 2,what started the process of the Moon's formation? 

A The collision of a large body with Earth 

B The melting of Earth's surface by the Sun 

C The collision of Mars with Earth 

D The explosion of a large body near Earth

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