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    4．According to the passage , in some areas if farmers who grow grapeslight fires in the early morning , that is because the farmers want to . A．drive away warm air B．prevent cold air from coming to harm their plants C．cause more wind D．stop warm air running away B Alzheimer’s disease is a major national health problem. Nearly 2 million Americans over the age of 65 have Alzheimer’s disease . It is a leading cause of death among the elderly . But Alzheimer’s disease is not confinedto the aged . There may be a million or more people under the age of 65 suffering from the disease . At one time , people suffering from the disease were said to be “getting old . The disease was thought to be a natural part of growing old , but it is now known that Alzheimer’s disease strikes young and old alike . It is an organicdisease that destroys brain cells . Alzheimer’s disease affects the patient’s memory , speech , and movement . In the beginning stages of the disease , the patient may seem slightly confused . He may have trouble speaking . Then the patient’s memory begins to fail . He may forget dates , telephone numbers , names and plans . As the disease progresses , the patient may not recognize family and friends . These symptomsoften cause terrible anxiety in the patient . He may feel lost and frightened . Sometimes the patient reacts with wild and bad behavior. In the last stages of the disease , the patient may not be able to take care of himself . He may have lost the ability to speak and walk . Scientists don’t know exactly what causes Alzheimer’s disease . It may be caused by a virus. It may be caused by a poisonous substancein the environment . At present, there is no cure for the disease . But there are ways to slow its progress . Exercise and physical treatment can help the patients of this disease . 【查看更多】

     

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    阅读下面短文，从每题所给四个选项中选出最佳答案。

    　　Without the atmosphere there would be no weather, no wind, rain, snow, or clouds. Air is all around us; we live at the bottom of a great ocean of air. It is invisible, but we can feel it when it moves. There are miles of air above us, pressing down with great weight on the earth and everything on it. Because air presses down on us from all directions at the same time, and because we are able to bear(忍受) this weight, we do not seem to feel it. But scientists have proved that air has this weight, and that anything that has weight creates(产生) a force called pressure. As changes in air pressure take place, they make air move.

    　　Air is a gas that expands(膨胀) when heated, gets lighter, and moves upward. When air is cooled, it gets heavier, sinks close to the earth's surface, and flows like water in a great river. As warm air rises, cold air rushes in to take its place. Thus winds originate(起源). The winds that blow high above us are caused by the warmer air running away from colder air. The wind we feel near the earth's surface is the heavy colder air trying hard to catch the warmer air. Changes in temperature cause the air to move. And of course there are many changes, so air movements are taking place practically all the time.

    1．The first paragraph mainly tells us the causes of ________.

    [　　]

    A．why we don't feel air

    B．why atmosphere is important to us

    C．why there is air surrounding us

    D．why there is air pressure

    2．Air moves under such conditions that ________.

    [　　]

    A．there is air pressure

    B．the air is heavy

    C．air pressure doesn't remain the same all the time

    D．air comes up and down

    3．According to the passage, in some areas if farmers who grow grapes(葡萄) light fires in the early morning, that is because the farmers want to ________.

    [　　]

    A．drive away warm air

    B．prevent cold air from coming to harm their plants

    C．cause more wind

    D．stop warm air running away

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