题目内容
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.
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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__
Astronomers and scientists think that a black hole is __2__a region of
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
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