欧美日韩黄网欧美日韩日B片|二区无码视频网站|欧美AAAA小视频|久久99爱视频播放|日本久久成人免费视频|性交黄色毛片特黄色性交毛片|91久久伊人日韩插穴|国产三级A片电影网站|亚州无码成人激情视频|国产又黄又粗又猛又爽的

There were lots of people _____， and not one of them offered to help.

A. standing watching               B. standing to watch

C. stood watching                 D. stood to watch

2. The boy slipped out of the room and headed for the swimming pool without his parents' _____.

A. command   B. conviction   C. consent  D. compromise

I have ___ work to do.

       A. a lot    B. lots    C.plenty of    D. many

Two ___ years ago she lived in New York.

        A.score     B.scores    C.scores of    D.score of

    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.

. I think Ma Linlin will ____ a good monitor, so I'm going to vote for her.

A. remain B. make C. get D. grow

The young couple decided to_____two homeless boys though they had three of their own.

  A. adapt     B. bring     C. receive     D. adopt

Although he has lived with us for years, he ______ us much impression.

A. hadn’t left     B. didn’t leave       C. doesn’t leave       D. hasn’t left

A new cinema ______ here. They hope to finish it next month.

A. will be built        B. is built      C. has been built      D. is being built

You know he is not going to let us leave early if we ___ get the work done.

A. can't B. may not C. shouldn't D. mustn't