B

　　(2009年南京二模)How many things can you see in the night sky？A lot! On a clear night you might see the Moon，some planets，and thousands of sparkling stars.

　　You can see even more with a telescope. And with bigger and bigger telescopes you can see more and more objects in the sky. And you can see those objects in more and more detail.

　　But scientists believe there are some things in the sky that we will never see. We won't see them with the biggest telescope in the world，on the clearest night of the year.

　　That's because they're invisible. They're the mysterious dead stars called black holes.

　　You might find it hard to imagine that stars die. After all，our Sun is a star. Year after year we see it up in the sky，burning brightly，giving us heat and light. The Sun certainly doesn't seem to be getting old or weak. But stars do burn out and die after billions of years.

　　As a star's gases burn，they give off light and heat. But when the gas runs out，the star stops burning and begins to die.

　　As the star cools，the outer layers of the star pull in toward the center. The star squashes into a smaller and smaller ball. If the star is very small，the star ends up as a cold，dark ball called a black dwarf. If the star is very big，it keeps squashing inward until it's packed together tighter than anything in the universe.

　　Imagine if the Earth were crushed until it was the size of a tiny marble. That's how tightly this dead star，a black hole，is packed. What pulls the star in toward its center with such power？It's the same force that pulls you down when you jump－the force called gravity. A black hole is so tightly packed that its gravity sucks in everything－even light. The light from a black hole can never come back to your eyes. That's why you see nothing but blackness.

　　So next time you stare up at the night sky，remember：there's more in the sky than we can see！Scattered in the silent darkness are black holes－the great mystery of space.

　　【解题导语】　每当你抬头仰望天空中闪烁的群星时，你是否知道在广袤的太空中还隐藏着无数我们无法看到的东西--黑洞。本文向读者介绍了这些黑洞的形成原因和过程。

　　5. According to the article，what causes a star to die?

　　A. As its gases run out，it cools down.

　　B. It has a collision with other stars.

　　C. It can only live for about a million years.

　　D. As it gets hotter and hotter，it explodes.

　　解析：选A。细节理解题。文章第六段讲述了其原因。当恒星周围的气体烧尽时，它便停止燃烧然后死亡。

　　6. Which of the following statements is NOT true?

　　A. Black holes are dead stars.

　　B. Black holes have gravity.

　　C. Black holes are invisible.

　　D. There is nothing as mysterious as a black hole.

　　解析：选D。细节理解题。文章只提到黑洞是宇宙中神秘的天体，但并没有说它是最神秘的东西。

　　7. What happens AFTER a star dies?

　　A. It becomes invisible.

　　B. It falls to the Earth.

　　C. It burns up all of its gases.

　　D. It becomes brighter and easier to see.

　　解析：选A。推理判断题。从第七、八段的内容可知A项正确。8. Why can't you see light when you look at a black hole?

　　A. Because most black holes are so far away.

　　B. Because the gravity of a black hole is so strong that it sucks the light inward.

C. Because as the star's gases burn，it stops giving off heat and light.