托福TPO71听力Lecture2原文+题目+答案+MP3音频下

托福TPO71听力Lecture2原文+题目+答案+MP3音频下

托福TPO71听力Lecture2原文：

Listen to part of a lecture in an astronomy class.

Before 1995, the only planets we knew about were those in orbit around our own sun. So, everything we thought we knew about planets was based on them, the planets here in our own solar system. The big question was, how did the planets form? And the prevailing theory back then, was the core accretion theory? According to the core accretion theory, when the sun formed in the middle of a huge, flat spinning disk of gas and dust, there were some leftovers, stuff that didn't go into making the sun. And as the disk kept swirling around bits of matter collided, and some stuck together in clumps. And over millions of years, some clumps gathered are created more and more material and eventually grew large enough to form rocky cores.

But um due to the sun's energy over long periods of time, the cores of planets closer to it, couldn't hold on to light gas very well. So they remained small, rocky planets like earth. Meanwhile, though the planets farther out from the sun, their gravitational force kept on pulling in gas molecules. These colder planets could have creat and hold on to huge amounts of gas. And you ended up with giant planets such as Jupiter, composed largely of gas.

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托福TPO71听力Lecture2题目如下：

(1)、(单选题) What is the mam purpose of the lecture?

A.To describe a recently discovered planet in orbit around a different sun

B.To demonstrate how gas giant planets such as Jupiter can change their orbits

C.To explain how the gas giant planets in our solar system were termed

D.To show the impact of a recent discovery on ideas about planet formation

(2)、(多选题) What does the core accretion theory predict based on the distance of planets from their sun?

A.Their relative sizes

B.Their approximate ages

C.Their general composition

D.Their gravitational effect on other planets

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