The surprising experiment I am about to describe proves that air is all around you and that it presses down upon you. Air pressure is a powerful force. When you swim underwater, you can feel water pushing down on your body. The air all around you does the same. However, your body is so used to it that you do not notice this. The pressure is caused by a layer of air called the atmosphere. This layer surrounds the Earth, extending to about five kilometers above the Earth’s surface.

    The following experiment is an easy one that you can do at home. But make sure that you are supervised, because you will need to use matches. Now for the experiment！

What you need

 ??A hard-boiled egg without the shell

 ??A bottle with a neck slightly smaller than the egg

 ??A piece of paper

 ??A match

 Method

 1） Check that the egg will sit firmly on the neck of the bottle.

 2） Tear the paper into strips and put the strips into the bottle.

 3） Light the paper by dropping a burning match into the bottle.

 4） Quickly sit the egg on the neck of the bottle.

Result

    Astonishingly, the egg will be sucked into the bottle. Your friends will be amazed when you show them the experiment. But be careful when you handle matches.

Why it happened

    As the paper burns, it needs oxygen and uses up the oxygen （air） in the bottle. The egg acts as a seal in the neck of the bottle, so no more air can get inside. This reduces the air pressure inside the bottle. The air pressure must equalize, so more air from outside must enter the bottle. The outside air pressure against the egg and then the egg is pushed into the bottle! This proves that air is all around and that it is pressing down on it.

Why is there the need to take care when you are doing the experiment?

 A. The bottle could break.

 B. You need to light the paper with a match.

 C. The egg needs to be shelled.

 D. The egg has to be perfectly placed on the neck of the bottle.

In the experiment, the burning inside the bottle can___.

 A. equalize the air pressure inside and outside

 B. make a seal in the neck of the bottle

 C. finish up the oxygen inside the bottle

 D. produce more oxygen inside the bottle

How did the egg put into the bottle？

 A. The oxygen inside the bottle sucked the egg in.

 B. It became saft without the shell.

 C. The neck of the bottle was wide enough.

 D. The outside air pressure forced it into the bottle.

The experiment is carried cut to prove ______.

 A. water pushes on your body when you swim underwater.

 B. the earth is surrounded by a layer of air called the atmosphere.

 C. the pressure of air around us has a powerful force.

 D. the air pressure is not equalized around us.

The surprising experiment I am about to describe proves that air is all around you and that it presses down upon you. Air pressure is a powerful force. When you swim underwater, you can feel water pushing down on your body. The air all around you does the same. However, your body is so used to it that you do not notice this. The pressure is caused by a layer of air called the atmosphere. This layer surrounds the Earth, extending to about five kilometers above the Earth’s surface.
The following experiment is an easy one that you can do at home. But make sure that you are supervised, because you will need to use matches. Now for the experiment！
What you need
?A hard-boiled egg without the shell
?A bottle with a neck slightly smaller than the egg
?A piece of paper
?A match
Method
1） Check that the egg will sit firmly on the neck of the bottle.
2） Tear the paper into strips and put the strips into the bottle.
3） Light the paper by dropping a burning match into the bottle.
4） Quickly sit the egg on the neck of the bottle.
Result
Astonishingly, the egg will be sucked into the bottle. Your friends will be amazed when you show them the experiment. But be careful when you handle matches.
Why it happened
As the paper burns, it needs oxygen and uses up the oxygen （air） in the bottle. The egg acts as a seal in the neck of the bottle, so no more air can get inside. This reduces the air pressure inside the bottle. The air pressure must equalize, so more air from outside must enter the bottle. The outside air pressure against the egg and then the egg is pushed into the bottle! This proves that air is all around and that it is pressing down on it.
【小题1】Why is there the need to take care when you are doing the experiment?

A．The bottle could break.

B．You need to light the paper with a match.

C．The egg needs to be shelled.

D．The egg has to be perfectly placed on the neck of the bottle.

【小题2】In the experiment, the burning inside the bottle can___.

A．equalize the air pressure inside and outside

B．make a seal in the neck of the bottle

C．finish up the oxygen inside the bottle

D．produce more oxygen inside the bottle

【小题3】How did the egg put into the bottle？

A．The oxygen inside the bottle sucked the egg in.

B．It became saft without the shell.

C．The neck of the bottle was wide enough.

D．The outside air pressure forced it into the bottle.

【小题4】The experiment is carried cut to prove ______.

A．water pushes on your body when you swim underwater.

B．the earth is surrounded by a layer of air called the atmosphere.

C．the pressure of air around us has a powerful force.

D．the air pressure is not equalized around us.

The surprising experiment I am about to describe proves that air is all around you and that it proves down upon you．Air pressure is a wonderful force．When you swim underwater, you can feel water push down your body．The air all around you does the same．However, your body is so used to it that you do not notice this．The pressure is caused by a layer of air called the atmosphere．This layer surrounds the Earth, extending to about five kilometers above the Earth's surface．

The following experiment is an easy one that you can do at home．But make sure that you are supervised, because you will need to use matches．

What you need

·A hard-boiled egg without the shell

·A bottle with a neck slightly smaller than the egg

·A piece of paper

·A match

Method

1）Check that the paper will sit firmly on the neck of the bottle．

2）Tear the paper into strips and put the strips into the bottle．

3）Light the paper by dropping a burning match into the bottle．

4）Quickly sit the egg on the neck of the bottle．

Result

Astonishingly, the egg will be sucked into the bottle．Your friends will be amazed when you show them the experiment．But be careful when you handle matches．

Why it happened

As the paper burns, it needs oxygen and uses up the oxygen （air）in the bottle．The egg acts as a seal in the neck of the bottle, so no more air can get inside．This reduces the air pressure inside the bottle．The air pressure must equalize, so more air from outside must enter the bottle．The outside air presses against the egg and then the egg is pushed into the bottle! That proves that air is all around and that it is pressing down on it．

Why is there the need to take care when you are doing the experiment?

A．The bottle could break．

B．You need to light the paper with a match．

C．The egg needs to be shelled．

D．The egg has to be perfectly placed on the neck of the bottle．

In the experiment, the burning inside the bottle can__．

A．equalize the air pressure inside and outside

B．make a seal in the neck of the bottle

C．finish up the oxygen inside the bottle

D．produce more oxygen inside the bottle

How did the egg put into the bottle?

A．The oxygen inside the bottle sucked the egg in．

B．It became salt without the shell．

C．The neck of the bottle was wide enough．

D．The outside air pressure forced it into the bottle．

The experiment is carried out to prove ____．

A．water pushes on your body when you swim underwater

B．the earth is surrounded by a layer of air called the atmosphere

C．the pressure of air around us has a powerful force

D．the air pressure is not equalized around us

The surprising experiment I am about to describe proves that air is all around you and that it proves down upon you．Air pressure is a wonderful force．When you swim underwater, you can feel water push down your body．The air all around you does the same．However, your body is so used to it that you do not notice this．The pressure is caused by a layer of air called the atmosphere．This layer surrounds the Earth, extending to about five kilometers above the Earth's surface．

The following experiment is an easy one that you can do at home．But make sure that you are supervised, because you will need to use matches．

What you need

·A hard-boiled egg without the shell

·A bottle with a neck slightly smaller than the egg

·A piece of paper

·A match

Method

1）Check that the paper will sit firmly on the neck of the bottle．

2）Tear the paper into strips and put the strips into the bottle．

3）Light the paper by dropping a burning match into the bottle．

4）Quickly sit the egg on the neck of the bottle．

Result

Astonishingly, the egg will be sucked into the bottle．Your friends will be amazed when you show them the experiment．But be careful when you handle matches．

Why it happened

As the paper burns, it needs oxygen and uses up the oxygen （air）in the bottle．The egg acts as a seal in the neck of the bottle, so no more air can get inside．This reduces the air pressure inside the bottle．The air pressure must equalize, so more air from outside must enter the bottle．The outside air presses against the egg and then the egg is pushed into the bottle! That proves that air is all around and that it is pressing down on it．

1.Why is there the need to take care when you are doing the experiment?

A．The bottle could break．

B．You need to light the paper with a match．

C．The egg needs to be shelled．

D．The egg has to be perfectly placed on the neck of the bottle．

2.In the experiment, the burning inside the bottle can__．

A．equalize the air pressure inside and outside

B．make a seal in the neck of the bottle

C．finish up the oxygen inside the bottle

D．produce more oxygen inside the bottle

3.How did the egg put into the bottle?

A．The oxygen inside the bottle sucked the egg in．[来源:学。科。网]

B．It became salt without the shell．

C．The neck of the bottle was wide enough．

D．The outside air pressure forced it into the bottle．

4.The experiment is carried out to prove ____．

A．water pushes on your body when you swim underwater

B．the earth is surrounded by a layer of air called the atmosphere

C．the pressure of air around us has a powerful force

D．the air pressure is not equalized around us

 

　　A historical change is taking place in middle-school education. Teachers are being asked to be responsible, as never before, for how well they serve their students. It has become as common in middle schools for students to grade teachers as for teachers to grade students. In fact, student ratings (评价) have become the most widely used and in many cases, the only important information on teaching effectiveness. In comparing three studies of the same 600 middle and high schools in more than thirty states, it was found that the number of schools using student ratings to evaluate (评估) teachers had climbed from 29 percent to 68 percent to 86 percent. No other method of evaluation got that degree of usage, and other studies have found similar results.

　　One reason that student evaluations of teachers have become so popular is that they are easy to carry out and to score. But they are also easy to put to wrong use. If they are expected to throw meaningful light on teachers' performance, the ratings must be used in a way that shows at least some of what we've learnt about them from research and from experience.

　　Research and experience have shown us, for example, that student ratings should never be the only basis for evaluating teaching effectiveness. There is much more to teaching than what is evaluated on student rating forms. When ratings are used, we know that students should not be expected to judge whether the materials used in a course are up to date (新颖的，时尚的) or how well the teacher knows the subject matter of the course. These judgments that require professional background are best left to the teacher's fellow workers. On the other hand, students should be asked to comment (评论) what they have learned in a course, and to report on such things as a teacher's ability to communicate at the students' level, general behavior in the classroom, relationship with the students, ability to develop interest in the subject and ways to encourage students to teach themselves.

(1) The central idea of the passage is that ________.

[　　]

A．student ratings are the only way to learn about teaching effectiveness

B．other methods are better than student ratings in evaluating teachers

C．it is quite right to make student ratings popular in the country

D．student ratings are very popular and should be properly used

(2) In Paragraph 2, the underlined expression "throw meaningful light on teachers' performance" means ________.

[　　]

A．judging teachers' teaching ability and understanding of the course

B．making teachers' performance clear and understood to all

C．having a main opinion of teachers' performance

D．speaking highly of the teachers' performance

(3) Which of the following statements can be inferred from the passage?

[　　]

A．Students should not be asked questions that require professional background.

B．Student evaluations are popular because they are extremely accurate.

C．Student ratings can be used in all the schools in any case.

D．Student ratings are already used in almost every school.

(4) In student ratings, one can not asked the question "________"

[　　]

A．Can the teacher make himself easily understood?

B．How does the teacher deal with the students?

C．Are students interested in what is taught?

D．Is what is taught by the teacher new?