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__
答案：
1 將as 改爲since或者because。在表示原因的連接詞中，只有as引導的原因狀語從句不能位於主句之後，只能位於句首。
2 將adequate 改爲inadequate，或者在are後加not。從邏輯上分析，因爲我們擁有的科學術語“不充足”，所以才無法回答這個問題，所以用否定形式。
3 在which 前加into。這是一個定語從句，意思是“黑洞是太空中物質可以掉進去的地方”，所以定語從句應該爲“into which matter has fallen”。
4 將but 改爲 so。 上文已提到“連光都無法從黑洞中逃出”，所以我們根本無法看到黑洞。這裏應該是因果關係，而不是轉折關係。
5 將thus改爲so。這句話的意思是“那只是空間—或者我們認爲它只是空間”。so做 think 的賓語，thus 只能做連詞，不能做賓語。
6 將which 改爲whose。這個定語從句的意思是“它是一顆星，其密度非常大，由於自身的'引力，它在不斷地收縮”。matter 屬於star，所以關係代詞應該用whose。
7 去掉in。result爲不及物動詞，意爲“形成了”，而“result in sth。”意爲“導致某結果”。
8 將masses 改爲mass。mass 可指“大量的物質”，而“the masses”特指“勞動羣衆”，用在此處不妥。
9 將ideas 改爲idea。“idea”在表達“印象”時，爲不可數名詞，不可以用複數。
10 將no改爲any。分析便知，任何在黑洞附近的東西都會被吸進去。
