【改错练习】
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
（责任编辑：liushengbao）
