【单选题】
{{B}}第一篇{{/B}}
If pollution continues to increase at the present rate, formation of aerosols (浮质) in the atmosphere will cause the onset (开始) of an ice age in about fifty year’s time. This conclusion reached byDr S. I. Rasoo1 andDr S. H. Scheider of the United States Goddard Space FlightCenter, answer the apparently conflicting questions of whether an increase in the carbon dioxide (二氧化碳) content of the atmosphere will cause theEarth warm up or increasing the aerosol question is dominant.
Two specters haunting conservationists have been the prospect that environmental pollution might lead to the planet’s becoming unbearably hot or colD、One of these ghosts has now been laid, because it seems that even an increase in the amount of carbon dioxide in the atmosphere to eight times its present value will produce an increase in temperature of only 2℃, which would take place over several thousand years.But the other problem now looms larger than ever.
Aerosols are collection of small liquid or solid particles dispersed in air or some other medium. The particles are all so tiny that each is composed of only a few hundred atoms.Because of this they can float in the air for a very long time. Perhaps the most commonly experienced aerosol is industrial smog (烟雾) of the kind that plagued London in the 1950s and is an even greater problem in LosAngeles today. These collections of aerosols reflect the Sun’s heat and thereby cause theEarth to cool.
Dr Rasoo1 andDr Schneider have calculated the exact effect of a dust aerosol layer just above theEarth’s surface in the temperature of the planet.As the layer builds up, the present delicate balance between the amount of heat absorbed from the Sun and the amount radiated from theEarth is disturbeD、The aerosol layer not only reflects much of the Sun’s light but also transmits the infrared (红外线) radiation from below. So, while the heat input to surface drops, the loss of heat remains high until the planet cools to a new balanced state.
Within fifty years, if no steps are taken to stop the spread of aerosols in the atmosphere, a cooling of theEarth by as much as 3.5~C、seems inevitable. If that lasts for only a few years it would start another ice age, and because the growing ice caps at each pole would themselves reflect much of the Sun’s radiation it would probably continue to develop even if the aerosol layer were destroyeD、
The only bright spot in this gloomy forecast lies in the hope expressed byDr Rasoo1 andDr Schneider that nuclear powder may replace fossil fuels in time to prevent the aerosol content of atmosphere from becoming critical.
B．"carbon dioxide"
C．"aerosols"
D．"ghosts"
网考网参考答案：D
网考网解析：
[解析] specter的基本含义是幽灵，而D的基本含义就是幽灵，所以可判断答案为D。也可借助上下文的语义关系判断。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>
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