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

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

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

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

The author mainly intended to tell us _____.

       A．A New Scientific Discovery: Black Holes

       B．How Black Holes Came Into Being

       C．What Black Holes Are

       D．Travel Through A Black Hole

D
There is probably no field of human activity in which our values and lifestyles are shown more clearly and strongly than they are in the clothes that we choose to wear. The dress of an individual is a kind of "sign language" that communicates a set of information and is usually the basis on which immediate impressions are formed. Traditionally, a concern for clothes was considered to be an affair of females, while men took pride in the fact they were completely lacking in clothes consciousness(意识).
This type of American culture is by degrees changing as man dress takes on greater variety and color. Even as early as 1995, a researcher in Michigan said that men attached rather high importance to the value of clothing in daily life. White－collar workers in particular viewed dress as a symbol of ability, which could be used to impress or influence others, especially in the work situation. The white－collar worker was described as extremely concerned about the impression his clothes made on his superiors(上司). Although blue－collar workers were less aware that they might be judged on the basis of their clothing, they recognized that any difference from the accepted pattern of dress would be made fun of by fellow workers.
Since that time, of course, the patterns have changed; the typical office worker may now be wearing the blue shirt, and the laborer a white shirt, but the importance of dress has not become less.      Other researchers in recent years have helped to prove its importance in the lives of individuals at various levels and in different social and economic status groups(阶层).
68．From the passage we know that______.
A．the Americans' values and lifestyles can't be shown clearly in their activity
B．the Americans' values and lifestyles are from the sign language
C．the clothes the Americans choose to wear have something to do with their values and lifestyles
D．the clothes the Americans choose to wear depend on a set of information
69．Traditionally, the Americans usually thought that______.
A．men should care much for clothes
B．women should concern greatly about what they wore but men shouldn't
C．both men and women must pay great attention to their clothes
D．neither men nor women didn't have to show interest in clothes
70．Blue－collar workers pay attention to their clothes because______.
A．they extremely concern about the impression their clothes make on their superiors
B．they know clearly that people will judge them on the basis of their clothing
C．they want to impress and influence others
D．they don't want to be laughed at
71．The passage mainly suggests that______.
A．the Americans pay great attention to the importance of clothes
B．now men in America have made more progress in clothes consciousness
C．now men in America care about clothes more than women do
D．the American culture is greatly changing