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__
参考谜底：
1 将as 改为since或者because。在暗示原因的毗连词中，只有as指导的原因状语从句不能位于主句之后，只能位于句首。
2 将adequate 改为inadequate，或者在are后加not。从逻辑上剖析，因为我们拥有的科学术语“不充沛”，所以才无法回覆这个问题，所以用否认形式。
3 在which 前加into。这是一个定语从句，意思是“黑洞是太空中物质可以失踪进去的处所”，所以定语从句应该为“into which matter has fallen”。
4 将but 改为 so。 上文已提到“连光都无法从黑洞中逃出”，所以我们根柢无法看到黑洞。这里应该是因不美观关系，而不是转折关系。
5 将thus改为so。这句话的意思是“那只是空间—或者我们认为它只是空间”。so做 think 的宾语，thus 只能做连词，不能做宾语。
6 将which 改为whose。这个定语从句的意思是“它是一颗星，其密度很是大，因为自身的引力，它在不竭地缩短”。matter 属于star，所以关系代词应该用whose。
7 去失踪in。result为不及物动词，意为“形成了”，而“result in sth。”意为“导致某结不美观”。
8 将masses 改为mass。mass 可指“大量的物质”，而“the masses”特指“劳动群众”，用在此处不妥。
9 将ideas 改为idea。“idea”在表达“印象”时，为不成数名词，不成以用复数。
10 将no改为any。剖析便知，任何在黑洞四周的工具城市被吸进去。