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.
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.
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 (挤压) into a smaller and smaller ball. If the star was very small, the star 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 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 remember: Scattered in the silent darkness are black holes—the great mystery of space.

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. D:Because as a star cools, its outer layers pull in toward its center.

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.
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.
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 (挤压) into a smaller and smaller ball. If the star was very small, the star 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 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 remember: Scattered in the silent darkness are black holes--the great mystery of space.

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. D:Because as a star cools, its outer layers pull in toward its center.

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.
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.
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 (挤压) into a smaller and smaller ball. If the star was very small, the star 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 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 remember: Scattered in the silent darkness are black holes--the great mystery of space.
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. D:Because as a star cools, its outer layers pull in toward its center.

Passage 2
It seems to shine unchangingly, pouring out a constant light year after year. But the sun may not be nearly so stable as we suppose. It is now thought to move quickly and irregularly and change in long-term cycles, growing dimmer and then brighter with each passing year. Some even fear that its frequent changing behavior would have a great influence on the Earth’ s climate.
The source of the sun’ s inconstancy is magnetism. Professor William Livingston has developed new theories about its magnetic nature.
"We don’ t yet know what causes sun spots, "he says, "but we now think they ’ re areas of high level magnetism that come up from the sun’ s interior. So strong is their magnetic pull that the highly ionized gas nearby is not able to transmit energy out. "As a result these areas send out less heat and light and thus appear from Earth to be almost dark irregular surface patches.
Sun spot activity generally fluctuates in steady, 11-year cycled. Scientists have long formed the o pinion that as the size and number of sun spots increased, the overall energy sent out by the sun would de crease. Indeed, recent studies confirmed it, revealing that during peak periods of sun spot activity, the Earth experiences a small drop that can be seen clearly in received solar energy.
Could such a small drop in energy have an effect here on earth Perhaps some scientists think the world temperature could fall by’ as much as 0.2 during periods of high solar magnetism.., enough to cause significant fluctuations in weather patterns.

Which of the following statements is supported by the passage（）

A:The sun shines constantly and gives out the same amount of energy every year. B:The cause of the sun' s fluctuations is its loss of energy with each passing year. C:It is sure that the energy sent out by the sun will drop when more sun spots appear. D:Fluctuations in weather patterns are the results of the pull of gravity.

It seems to shine unchangingly, pouring out a constant light year after year. But the sun may not be nearly so stable as we suppose, It is now thought to move quickly and irregularly and change in long-term cycles, growing dimmer and then brighter with each passing year. Some even fear that its frequent changing behavior would have a great influence on the Earth’s climate.
The source of the sun’s inconstancy is magnetism. Professor William Livingston has developed new theories about its magnetic nature.
"We don’t yet know what causes sun spots, "he says, "but we now think they’re areas of high-level magnetism that come up from the sun’s interior. So strong is their magnetic pull that the highly ionized gas nearby is not able to transmit energy out." As a result these areas send out less heat and light and thus appear from Earth to be almost dark irregular surface patches.
Sun spot activity generally fluctuates in steady, 11-year cycled. Scientists have long formed the opinion that as the size and number of sun spots increased, the overall energy sent out by the sun would decrease. Indeed, recent studies confirmed it, revealing that during peak periods of sun spot activity, the Earth experiences a small drop that can be seen clearly in received solar energy.
Could such a small drop in energy have an effect here on earth Perhaps some scientists think the world temperature could fall by as much as 0.2 during periods of high solar magnetism... enough to cause significant fluctuations in weather patterns.
Which of the following statements is supported by the passage ______

A:The sun shines constantly and gives out the same amount of energy every year. B:The cause of the sun’s fluctuations is its loss of energy with each passing year. C:It is sure that the energy sent out by the sun will drop when more sun spots appear. D:Fluctuations in weather patterns are the results of the pull of gravity.

Passage Two

Which of the following statements is supported by the passage ______

A:The sun shines constantly and gives out the same amount of energy every year. B:The cause of the sun’s fluctuations is its loss of energy with each passing year. C:It is sure that the energy sent out by the sun will drop when more sun spots appear. D:Fluctuations in weather patterns are the results of the pull of gravity.

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.
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.
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 (挤压) into a smaller and smaller ball. If the star was very small, the star 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 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 remember: Scattered in the silent darkness are black holes--the great mystery of space.

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. D:Because as a star cools, its outer layers pull in toward its center.

We do not feel the gravitational pull of a packet of butter because

A:it is too small to have a gravitational pull of its own. B:its pull is so small that we tend to ignore it. C:its pull disappears in the presence of the earth's gravitation. D:it tends to melt and loses its gravitational pull.

We do not feel the gravitational pull of a packet of butter because

A:it is too small to have a gravitational pull of its own. B:its pull is so small that we tend to ignore it. C:its pull disappears in the presence of the earth's gravitation. D:it tends to melt and loses its gravitational pull.