專八模擬改錯(9)

What is a black hole? Well, it is difficult to answer the question,
as the terms we would normally use to describe a scientific phenomenon __1__
are adequate here. Astronomers and scientists think that a black hole is __2__
a region of space which matter has fallen and from which nothing can __3__
escape—not even light. But we can’t see a black hole. A black hole __4__
exerts a strong gravitational pull and yet it has no matter. It is only
space—or thus we think. How can this happen? __5__
The theory is that some stars explode when their density increases
to a particular point; they “collapse” and sometimes a supernova occurs.
The collapse of a star may produce a “White Dwarf” of a “neutronstar”—
a star which matter is so dense that if continually shrinks by the force of __6___
its own gravity. But if the star is very large, this process of shrinking may
be so intense that a black hole results in. Imagine the earth reduced to the __7__
size of a marble, but still having the same masses and a stronger __8__
gravitational pull, and you have some ideas of the force of a black hole. __9__
And no matter near the black hole is sucked in. __10__

（責(zé)任編輯：liushengbao）