阅读下列短文，从所给的四个选项中，选出最佳答案

　Gravity holds us so close to the earth's surface that nobody can jump more than a few feet into the air with the force of gravity pulling him down．It takes a powerful engine to keep an aeroplane up in the air．If you throw a ball upwards as hard as you can, you will notice that it travels in a curved（弯曲的）path before it comes back to the ground．If the earth had no gravity, the ball, instead of traveling in a curve, would move away in a straight line; in fact, it would never come back to the ground．If the earth were to lose its pull of gravity, we should all fly off it as it spins（旋转）round in space．The earth has a strong pull, but modern rockets going out into space are able to escape from the gravity, because they travel so quickly．With the ball thrown into the air, the height reached by the ball depends upon how hard it is thrown．The greater the starting speed, the higher the ball will go．If it could be thrown so that it travelled fast enough, the ball would escape into space and never come back．Nobody can throw a ball as fast as this, but powerful rocket engines can send spaceships away from the earth at such a speed that the earth's gravity is not able to pull them back．This is how we can now send rockets to the moon．

(1) Gravity holds us close to the earth's surface, and as a result, ______．

[　　]

A．we can lift ourselves no more than a few feet above the earth

B．nobody can jump a few feet into the air

C．no one will be pulled down

D．any one of us can jump as high as expected

(2) If there were no gravity, a ball thrown upwards would ______．　　　

[　　]

A．spin round in space

B．fall in a curved path

C．fly off into space

D．move towards the earth

(3) The ball thrown into the air would never come back to the ground ______．

[　　]

A．without a powerful push

B．if it were thrown upwards as hard as you can

C．should it travel in a curved path

D．were it not for gravity

(4) The height the ball will reach depends on ______．

[　　]

A．the escape speed

B．its starting speed

C．the limiting speed

D．its traveling speed

(5) What is it that makes it possible to put a spaceship into orbit（轨道）?

[　　]

A．The earth's gravity

B．A powerful engine

C．A strong pull

D．The powerful rocket engine

Even if  you are a good high-jumper, you can jump only about seven feet off the ground. You cannot jump any higher because the earth pulls you hard. The pull of the earth is called gravity.

   You can easily find out the pull of the earth. If you weigh yourself, you will know how much gravity is pulling you. 来源：

   Since there is gravity, water runs down hill. When you throw a ball into the air, it falls back down. Because of gravity, you do not fall off the earth as it whirls (旋转) around. 来源：

   Then, can we get away from the earth and go far out into space? Now you can do it, because spaceships have been invented. Then spaceship will go so fast that it can escape (逃出) the earth’s gravity and carry you into space. 来源：

In this passage, the word “gravity” means_______.来源：

   A. the pull of everything.           B. the force of attraction(吸引) among objects.

   C. the force which attracts objects towards the centre of the earth来源：

   D. the force which attracts the earth towards the sun.

When you slip(滑) you always fall to the ground because________来源：

   A. the earth always turns round.                   B. the earth has gravity

   C. the earth’s gravity is greater than your weight.     D. you are careless. 来源：

Gravity is strong that_______

   A. it can throw a ball into the air.           B. it makes you jump only seven feet.

   C. it can let you fly away from the earth.     D. it can keep everything on earth.

Because of gravity,________

   A. water flows everything.            B. we can go everywhere by ship. 来源：

   C. water always flows downwards.     D. fish can live in water.

We can get away from the earth by spaceship because________

   A. the spaceship goes very fast.       B. the earth can’t pull the spaceship.

C. the spaceship has a strong force.    D. the spaceship can jump higher than others.

阅读理解

阅读下列短文，从每题所给的四个选项（A、B、C和D）中；选出最佳选项。

　　Even if you are a good high－jumper, you can jump only about seven feet off the ground. You cannot jump any higher because the earth pulls you hard. The pull of the earth is called gravity.

　　You can easily find out the pull of the earth. If you weigh yourself, you will know how much gravity is pulling you.

　　Since there is gravity, water runs downhill. When you throw a ball into the air, it falls back down. Because of gravity you do not fall off the earth as it whirls(旋转) around.

　　Then, can we get away from the earth and go far out into space? Now you can do it, because spaceships have been invented. The spaceship will go so fast that it can escape the earth's gravity and carry you into space.

1．In this passage, the word “gravity” means ________.

[　　]

A．the force of attraction(吸引力) among objects

B．the pull of everything

C．the force which attracts objects towards the centre of the earth

D．the force which attracts the earth towards the sun

2．When you slip(滑倒) on something, you ________.

[　　]

A．always fall down to the ground

B．sometimes fall down to the ground

C．go up into the air

D．never fall down to the ground

3．Gravity is so strong that ________.

[　　]

A．it can throw a ball into the air

B．it makes you jump only seven feet

C．it makes you go up into the air

D．it can keep everything on earth

4．________ because gravity pulls it.

[　　]

A．Water flows everywhere

B．Water flows downwards on the earth's surface(表面)

C．We can go everywhere by ship

D．Fish can live in water

V.阅读理解 (共两节，满分30)

第一节（共10小题，每小题2分，满分20分）

Even if  you are a good high-jumper, you can jump only about seven feet off the ground. You cannot jump any higher because the earth pulls you hard. The pull of the earth is called gravity.

   You can easily find out the pull of the earth. If you weigh yourself, you will know how much gravity is pulling you. 

   Since there is gravity, water runs down hill. When you throw a ball into the air, it falls back down. Because of gravity, you do not fall off the earth as it whirls (旋转) around. 

   Then, can we get away from the earth and go far out into space? Now you can do it, because spaceships have been invented. Then spaceship will go so fast that it can escape (逃出) the earth’s gravity and carry you into space. 

31. In this passage, the word “gravity” means_______.  

   A. the pull of everything.           B. the force of attraction(吸引) among objects.

   C. the force which attracts objects towards the centre of the earth

   D. the force which attracts the earth towards the sun.

32. When you slip(滑) you always fall to the ground because________

   A. the earth always turns round.                   B. the earth has gravity

   C. the earth’s gravity is greater than your weight.     D. you are careless. 

33. Gravity is strong that_______

   A. it can throw a ball into the air.           B. it makes you jump only seven feet.

   C. it can let you fly away from the earth.     D. it can keep everything on earth.

34. Because of gravity,________

   A. water flows everything.            B. we can go everywhere by ship. 

   C. water always flows downwards.     D. fish can live in water.

35. We can get away from the earth by spaceship because________

   A. the spaceship goes very fast.       B. the earth can’t pull the spaceship.

C. the spaceship has a strong force.    D. the spaceship can jump higher than others.