What is a black hole? Well, it is difficult to answer this question, since the terms we would normally use to describe a scientific phenomenon are inadequate here. 1) __________________________________________________. A black hole exerts a strong gravitational pull and yet it has no matter. It is only space —— or so we think. How can this happen?
2) __________________________________________________. From earth, a supernova looks like a very bright light in the sky that shines even in the daytime. Supernova was reported by astronomers in the seventeenth and eighteenth centuries. Some people think that the Star of Bethlehem could have been a supernova. The collapse of a star may produce a White Dwarf of a neutron star —— a star, whose matter is so dense that it continually shrinks by the force of its own gravity. But if the star is very large (much bigger than our sun), this process of shrinking may be so intense that a black hole results. 3) __________________________________________________. Amy matter near the black hole is sucked in. It is impossible to say what happens inside a black hole. Scientists have called the boundary area around the hole the “event horizon”. We know nothing about events that happen once objects pass this boundary. But in theory, matter must behave very differently inside the hole.
4) __________________________________________________. Our space and time laws don't seem to apply to objects in the area of a black hole. Einstein claimed that matter and energy are interchangeable, so that there is no “absolute” time and space. There are no constants at all, and measurements of time and space depend on the position of the observer. They are relative. We do not yet fully understand the implications of the relativity theory; but it is interesting that Einstein's theory provided a basis for the idea of black holes before astronomers started to find some evidence for their existence. It is only recently that astronomers have begun specific research into black holes. 5 ) __________________________________________________.
The most convincing evidence of black holes comes from research into binary star systems. Binary stars, as their name suggests, are twin stars whose position in space affects each other. In some binary systems, astronomers have shown that there is an invisible companion star, a “partner” to the one that we can see in the sky. Matter from the one that we can see is being pulled towards the companion star. Should this invisible star, which exerts such a great force be a black hole? Astronomers have evidence of a few other stars too, which might have black holes as companions.
The story of black holes is just beginning. Speculations about them are endless.
[A] For example, if a man fell into a black hole, he would think that he reached the center of it very quickly. However, an observer at the event horizon would think that the man never reached the center at all.
[B] There might be a massive black hole at the center of our galaxy swallowing up stars at a very rapid rate.
[C] The theory is that some stars explode when their density increases to a particular point; they collapse and sometimes a supernova occurs.
[D] In August 1977, a satellite was launched to gather data about the 10 million black holes that are thought to be in the Milky Way. And astronomers are planning a new observatory to study the individual exploding stars believed to be black holes.
[E] Imagine the earth reduced to the size of a marble, but still having the same mass and a strong gravitational pull, and you have some idea of the force of a black hole.
[F] The theory of black holes in space is accepted by many serious. Scientists and astronomers. They show us a world that operates in a totally different way from our own and they question our most basic experience of space and time.
[G] Astronomers and scientists think that a black hole is a region of space ( not a thing) into which matters have fallen and from which nothing can escape - not even light. So we can't see a black hole.
2) 【答案】[C]。本题在文章第二自然段的开始。在上一段提出了黑洞是如何产生的问题。本段是上一段的延续和扩展，要在理论上对黑洞进行解释。再看问题后面的内容，讲到超新星：From earth, a supernova looks like a very bright light in the sky that shines even in the daytime.（从地球上看，一个超新星就像天空中一束明亮的光，有时甚至在白天也很耀眼）。这正是选项[C]内容的延续和扩展，两者正好形成顺承关系。所以，选项[C]是正确答案。
3) 【答案】[E]。本题在第二自然段的.中间。要根据上下文来判断其内容，而后进行选择。上文提到了黑洞的产生，下文提到了靠近黑洞的任何物质都被吸进去，可以推断空白处还应该是与黑洞的吸力有关的内容。这样，行文才连贯，结构才严谨，意义才流畅。选项[E]讲：设想一下地球缩小到弹子球的大小，但仍然有同样的质量和引力，你就能对黑洞的力量有所了解了（Imagine the earth reduced to the size of a marble，but still having the same mass and a strong gravitational pull，and you will have some idea of the force of a black hole．）。正符合这些要求，所以选项[E]是正确答案。
4) 【答案】[A]。本题在一个段落的开始。上一段最后讲到：物体一旦跨过边缘之后，我们就不知道发生了什么。但从理论上讲，物质在黑洞内的表现会明显不同（We know nothing about events that happen once objects pass this boundary. But in theory, matter must behave very differently inside the hole.）。空白后面的内容是：我们的“时间和空间法则”并不适合于黑洞内的物质。并进一步用Einstein的相对论来证明这一点。由此推断，空白处应该用一个通俗易懂的例子来进一步解释这些理论。选项[A]就是以一个进入黑洞的人和一个观察者的不同感觉来说明这一点。选项[A]与前面的内容形成例证关系。前面提出观点，接着给出论证。所以，[A]是正确答案。
5) 【答案】[D]。本题要与上一题结合起来解答，因为本题在上题所在段落的结尾处。该段以论证说明我们的时空法则不适合于黑洞里的物质，接着又讲到：爱因斯坦的理论在天文学家拿出证据证明黑洞的存在之前就提供了理论基础。只是最近天文学家才开始对黑洞进行具体研究（but it is interesting that Einstein's theory provided a basis for the idea of black holes before astronomers started to find some evidence for their existence. It is only recently that astronomers have begun specific research into black holes.）。根据上文的内容，我们可以推断，下面应该以具体的事实或例证来说明最近天文学家对活动做了哪些具体的研究。选项[D]正是这样的内容：“1977年发射的一颗人造卫星收集到了关于银河系一千万个黑洞的数据。天文学家正在计划建造一个新的天文站来观测被认为是黑洞的单个爆炸星体。”选项[D]与前文有着论证关系，衔接得非常自然。所以，选项[D]是正确答案。