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  3. Black Holes 1 Black holes can be best described as a sort of vacuum，sucking ...

Black Holes 1 Black holes can be best described as a sort of vacuum，sucking ...

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问题 Black Holes
1 Black holes can be best described as a sort of vacuum，sucking up everything in space. Scientists have discovered that black holes come from an explosion of huge stars. Stars that are near death can no longer bum due to loss of fuel，and because its temperature can no longer control the gravitational (重力的）force，hydrogen ends up putting pressure onto the star’s surface until it suddenly explodes then collapses.
2 Black holes come 什om stars that are made of hydrogen，other gases and a few metals. When these explode it can turn into a stellar-mass (恒星质量）black hole，which can only occur if the star is large enough (should be bigger than the sun) for the explosion to break it into pieces， and the gravity starts to compact every piece into the tiniest particle. Try to see and compare: if a star that’s ten times the size of the sun ends up being a black hole that’s no longer than 70 kilometers, then the Earth would become a black hole that’s only a fraction of an Inch!
3 Objects that get sucked in a black hole will always remain there，never to break free. But remember that biack holes can only gobble up (吞噬）objects within a specific distance to it. It’s possible for a large star near the sun to become a black hole，but the sun will continue to stay in place. Orbits do not change because the newly formed b丨ack hole contains exactly the same amount of mass as when it was a star，only this time its mass is totally contracted that it can end up as no bigger than a state.
4 So far，astronomers have figured out that black holes exist because of Albert Einstein’s theory of relativity.In the end，through numerous studies，they have discovered that black holes truly exist. Since black holes trap light and do not give off light, it is neatly impossible to detect black holes via a telescope. But astronomers continue to study galaxies， space and the solaf system to understand how b丨ack holes might evolve.It is possible that black holes can exist for millions of years, and later contribute to a bigger process in galaxies, which can eventually lead to creation of new entities. Scientists also credit black holes as helpful in learning how galaxies began to form.
选项 A How are black holes formed?
B What are black holes made of?
C How were black holes named?
D What are different types of black holes?
E Is there proof that black holes really exist?
F What happens to the objects around a black hole?
Paragraph 2___
答案B
解析本段的主题句是 “Black holes come from stars that are made of hydrogen，other gases and a few metals”，意为“黑洞来源于由氢气、其他气体和少量金属组成的星体”，本段其他的句子在讲黑洞的形成条件。所以本段主要讲的是黑洞的组成。答案是B。
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