ends up as a cold dark ball called a black dwarf. If the star was very big it keeps squashing inward until it's packed together tighter than anything in the universe.

　　 Imagine if the Earth was 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 towards its centre 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 the next time you stare up at the night sky remember：there's more in the sky than meets the eye! Scattered in the silent darkness are black holes-the great mystery of space.

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

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

　　 B．It collides(碰撞) with other stars.

　　 C．The star pulls in towards the centre.

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

　　解析：细节理解题。由第五段第二句话"But when the gas runs out，..."可知答案。

　　答案：A

　　6．Which of the following statements is NOT a fact?

　　 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：推理判断题。文章中六、七、八段中有对四个选项的介绍，可推知A、B、C三个选项是正确的，D项是主观推断，文中并无确切信息。

　　答案：D

　　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：细节理解题。由第七段中最后两句话"The light from a black hole can never come back to your eyes. That's why you see nothing but blackness."可知答案。

　　答案：A

　　8．We can't see light when we look at a black hole because ________.

　　 A．most black holes are so far away

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

　　 C．as the star's gas runs out，it stops giving off heat and light

　　 D．as a star cools，its outer layers pull in towards its centre

解析：细节理解题。第七段中"A black hole is so tightly packed that ...even