A black hole is created when a large star burns out. Like our sun, stars are unbelievably hot furnaces(熔炉) that burn their own matter as fuel. When most of the fuel is used up, the star begins to die.

The death of a star is not a quiet event. First there is a huge explosion. As its outer layer is blasted off into space, the dying star shines as brightly as a billion suns.

After the explosion gravity pulls in what’s left of the star. As the outside of the star sinks toward the center, the star gets smaller and smaller. The material the star is made of becomes tightly packed together. A star is so dense that a teaspoon of matter from it weighs billion of pounds.

The more the star shrinks, the stronger the gravity inside it becomes. Soon the star is very tiny, and the gravity pulling it in is unbelievably strong. In fact, the gravity is so strong that it even pulls light into the star! Since all the light is pulled in, none can go out. The star becomes black when there is no light. Then a black hole is born!

That’s what we know about black holes. What we don’t know is this: What happens inside a black hole after the star has been squeezed into a tiny ball? Does it keep getting smaller and smaller forever? Such a possibility is hard to imagine.

But if the black hole doesn’t keep shrinking, what happens to it? Some scientists think black holes are like doorways to another world．They say that as the star disappears from our universe, it goes into another universe. In other words a black hole in our universe could turn into a “white hole” in a different universe. As the black hole swallows light, the white hole shines brightly — somewhere else. But where? A different place, perhaps, or a different time — many years in the past or future.

Could you travel through a black hole? Right now, no. Nothing we know of could go into a black hole without being crushed．So far the time being, black hole must remain a mystery.

Black holes are a mystery—but that hasn’t stopped scientists from dreaming about them. One scientist suggested that in the future we might make use of the power of black holes. They would supply all of Earth’s energy needs, with plenty to spare. Another scientist wondered if a black hole could some day be used to swallow earthly waste—a sort of huge waste disposal (处理) in the sky!

When the star begins to die ______.

       A．there is no fuel left in it B．its outer layer goes into space first

       C．a huge explosion will happen        D．it doesn’t give off light any longer

Which of the following doesn’t help produce a black hole?

       A．The gravity inside the star is very strong.

       B．The light can’t go out of the star.

       C．The star becomes smaller and smaller

       D．The dying star shines very brightly.

The black hole ______.

       A．continues becoming smaller and smaller all the time

       B．goes into another universe and becomes a white hole

       C．can pull in everything we know of in the world

       D．will appear at another place at a different time

What’s the best title for this passage?

       A．A New Scientific Discovery: Black Holes

       B．How Do Black Holes Come Into Being?

       C．What Are Black Holes?

       D．Travel Through A Black Hole

Atomic energy has _____ many uses, either as fuel or as radiation, _____ it is almost impossible to imagine all the great changes it will bring into our lives.

a. such…as                   b. such…that         c. too…then                  d. so…that

Everywhere man has cut down           forests in order to grow crops, or to use               .

       wood as fuel or as building material.

       A．the; the                                               B．the;/

       C．/ ; the                                                 D．/ ; /

Everywhere man has cut down_______forests in order to grow crops,or to use_______wood as fuel or as building material.

A.the;the               B.the;/                   C./;the                   D./;/

     As skies are filled with millions of migrating(迁徙)birds, European scientists say the seasonal wonder appears to be strange: The fatter the bird, the better it flies.

     The results of their study led to a theory opposite to a central one of aerodynamics(空气动力学), which says that the power needed to fly increases with weight.

     For birds, obviously, the cost of flying with heavy fat is much smaller than we used to think. Researchers found that red knot wading birds double their normal body weight of 100 grams before making their twice-a-year nonstop flight between the British Isles and the Russian Arctic. Distance: 5, 000 kilometers.

     Another study in the magazine Nature measured the advantage of flying in an aerodynamic group which allows birds to save energy by flying smoothly and quietly in the lead bird’s air stream.

     Flying in groups, their heart rates were 14.5 percent lower than flying alone, according to Henri, a French scientist. The findings help explain how birds complete difficult migrations. Researchers had thought that thinner, stronger birds would have the best chance  to survive.

       The first study suggests that building up fat to be burnt as fuel during the migration is worth more than the energy it takes to carry the additional weight.

       In the study, researchers said their team studied the birds flown at different body weights during 28 simulated(模拟的)flights. They forced a small amount of special water into the birds’ bodies so that they could measure the amount of energy burnt during the flight.

60.A red knot wading bird of 100 grams will probably weigh_____before making its nonstop migrating flight.

A.50 grams             B.100 grams           C.150 grams             D.200 grams

61.During their migrating flight, red knot wading birds can save energy by flying_______.

A.separately        B.alone            C.in groups               D.in pairs

62.A_______red not wading bird has a better chance to survive during its migrating flight.

 A.stronger       B.weaker         C.thinner                   D.fatter

63.The best title for this passage may probably be________.

A.Birds Thin Down For Journey                B.Birds Fatten Up For Journey

C.How Birds Build Up Fat For Journey       D.How Birds Burn Energy For Journey