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oxygen

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1.On a hydrocarbon flammability chart the line which extends from 0% to 21.8% oxygen，lying tangent to the flammability range，is called the ______．A.minimum oxygen content lineB.critical displacement lineC.critical dilution lineD.upper threshold limit

2.Passage 2 If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21st century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan. Sagan believes that before the earth's resources are completely exhausted it will be possible to change the atmosphere of Venus and so create a new world almost as large as earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there. Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon. When the algae have done their work, the atmosphere will become cooler, but before man can set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus. On Venus there is a lot of__________.A. water B. carbon dioxide C. carbon monoxide D. oxygen

3.Passage 2 If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21st century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan. Sagan believes that before the earth's resources are completely exhausted it will be possible to change the atmosphere of Venus and so create a new world almost as large as earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there. Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon. When the algae have done their work, the atmosphere will become cooler, but before man can set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus.On Venus there is a lot of__________. 查看材料 A．water B．carbon dioxide C．carbon monoxide D．oxygen

4.______is not one of the most important environmental factors that influence hydrocarbon biodegradation．A.temperatureB.concentration of nutrientsC.nitrogenD.oxygen

更多“oxygen ”相关问题

  • 第1题：

    Vitamins are similar because they are made of the same elements—usually carbon,hydrogen,oxygen,and sometimes nitrogen.They are different in that their elements are arranged differently,and each vitamin been（ ）one or more specific functions in the body.

    A.holds
    B.plays
    C.performs

    答案：A
    解析：
    根据句意，所选项要有“起作用”的含义。四个选项中，只有D.perform“执行，履行”与function相搭配，意为“起作用”。A.undertake“着手，承担”；B.hold“抓住，掌握”；C.play常和part或role搭配，也可表达“起作用”之意。

  • 第2题：

    On Venus there is a lot of__________.

    A.water
    B.carbon dioxide
    C.carbon monoxide
    D.oxygen

    答案：B
    解析：
    由第二段的最后一句话中的“there is only a tiny amount of water there(Venus)”得知，A选项错误。第三段结尾说明，藻类通过火箭运往金星，然后“In a fairly short time，the algae will break down thecarbon dioxide into oxygen and carbon”，说明金星上有大量的二氧化碳。C和D选项错误。故选B。

  • 第3题：

    共用题干
    第二篇

    Superconducting Ceramic（陶瓷）

    An underaround revolution beqins this winter. With the flip（轻击）of a switch,
    30,000 homes in one part of Detroit will soon become the first in the country to receive
    electricity transmitted by ice-cold high-performance cables.Other American cities are
    expected to follow Detroit's example in the years ahead,which could conserve enormous
    amounts of rower.
    The new electrical cables at the Frisbie power station in Detroit are revolutionary
    because they are made of superconductors.A superconductor is a material that transmits
    electricity with little or no resistance.Resistance is the degree to which a substance resists
    electric current.All common electrical conductors have a certain amount of electrical
    resistance.They convert at least some of the electrical energy passing through them into
    waste heat.Superconductors don't.No one understands how superconductivity works.It
    just does.
    Making superconductors isn't easy.A superconducting material has to be cooled to an
    extremely low temperature to lose its resistance.The first superconductors,made more
    than 50 years ago,had to be cooled to -263 degrees Celsius before they lost their
    resistance.Newer superconducting materials lose their resistance at-143 degrees Celsius.
    The superconductors cable installed at the Frisbie station is made of a ceramic material
    that contains copper,oxygen,bismuth（秘）,strontium（锶）and calcium (钙）.A
    ceramic is a hard,strong compound made from clay or minerals.The superconducting
    ceramic has been fashioned into a tape that is wrapped lengthwise around a long tube filled
    with liquid nitrogen.Liquid nitrogen is supercold and lowers the temperature of the ceramic
    tape to the point where it conveys electricity with zero resistance.
    The United States loses an enormous amount of electricity each year to resistance.
    Because cooled superconductors have no resistance,they waste much less power. Other
    cities are watching the Frisbie experiment in the hope that they might switch to
    superconducting cable and conserve power,too.

    According tothe last paragraph,which of the following statements is NOT true?
    A:Other cities hope they can also conserve power.
    B:Other cities hope they can use superconducting cables soon.
    C:Superconductors waste less power because of their low resistance.
    D:The Frisbie experiment is not successful.

    答案：D
    解析：

  • 第4题：

    If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet.By the middle of the 21st century,if present trends continue, we will have used up all the oil that drives our cars,for example.Even if scientists develop new ways of feeding the human race,the crowded conditions on earth will make it necessary for lus to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however,has recently been suggested by American scientist, Professor Carl Sagan.
    Sagan believes that before the earth's resources are compleetely exhausted it will be possible to change the atmophere of Venus and so create a new world almost as large as earth itself. The difficult is that Venus is much hotter than the earth and there is only a tiny amount of water there.
    Sagan proposes that algae organisms that can live in extremely hot or cold atmospheres and at the same time produce oxygen,should be bred in condition similar to those on Venus.As soon as this has been done, the algae will be placed in small rockets. Spaceship will then fly to Venus and fire the rockets into the atmosphere .In a fairly short time, the alge will break down the carbon dioxide into oxygen and carbon.
    When the algae have done theri work, the atmosphere will become cooler,but befor man can set foot on Venus it will be neccessary for the oxygen to produce rain. The surface of the planet will still be too hot for man to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus.
    On Venus there is a lot of ________.

    a.water
    b.carbon dioxide
    c.carbon monoxide
    d.oxygen

    答案：B
    解析：

  • 第5题：

    共用题干
    第二篇

    Superconducting Ceramic（陶瓷）

    An underaround revolution beqins this winter. With the flip（轻击）of a switch,
    30,000 homes in one part of Detroit will soon become the first in the country to receive
    electricity transmitted by ice-cold high-performance cables.Other American cities are
    expected to follow Detroit's example in the years ahead,which could conserve enormous
    amounts of rower.
    The new electrical cables at the Frisbie power station in Detroit are revolutionary
    because they are made of superconductors.A superconductor is a material that transmits
    electricity with little or no resistance.Resistance is the degree to which a substance resists
    electric current.All common electrical conductors have a certain amount of electrical
    resistance.They convert at least some of the electrical energy passing through them into
    waste heat.Superconductors don't.No one understands how superconductivity works.It
    just does.
    Making superconductors isn't easy.A superconducting material has to be cooled to an
    extremely low temperature to lose its resistance.The first superconductors,made more
    than 50 years ago,had to be cooled to -263 degrees Celsius before they lost their
    resistance.Newer superconducting materials lose their resistance at-143 degrees Celsius.
    The superconductors cable installed at the Frisbie station is made of a ceramic material
    that contains copper,oxygen,bismuth（秘）,strontium（锶）and calcium (钙）.A
    ceramic is a hard,strong compound made from clay or minerals.The superconducting
    ceramic has been fashioned into a tape that is wrapped lengthwise around a long tube filled
    with liquid nitrogen.Liquid nitrogen is supercold and lowers the temperature of the ceramic
    tape to the point where it conveys electricity with zero resistance.
    The United States loses an enormous amount of electricity each year to resistance.
    Because cooled superconductors have no resistance,they waste much less power. Other
    cities are watching the Frisbie experiment in the hope that they might switch to
    superconducting cable and conserve power,too.

    What is the benefit of the revolution mentioned in the first paragraph?
    A:With a flip of switch,electricity can be transmitted,
    B:Other American cities can benefit from the high-performance cables.
    C:Great amounts of power can be conserved.
    D:Detroit will first receive electricity transmitted by the new electrical cables.

    答案：C
    解析：

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