专四专八考试

【单选题】If pollution continues to increase at the present rate, formation of aerosols in the atmosphere will cause the onset of an ice age in about fifty years’ time. This conclusion, reached byDr. S. I. Rasool andDr. S.H. Schneider of the United States Goddard Space FlightCentre, answers the apparently conflicting questions of whether an increase in the carbon dioxide content of the atmosphere will cause theEarth to warm up or increasing the aerosol content will cause it to cool down. TheAmericans have shown conclusively that 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 collections 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 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. Rasool 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 radiation from below. So, while the heat input to the 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 ℃ 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. Rasool andDr. Schneider that nuclear power may replace fossil fuels in time to prevent the aerosol content of the atmosphere from becoming critical.
We can infer from the passage that ______.
A、there is no need to worry about the problem of aerosols
B．the problem of aerosols is much more serious than the problem of carbon dioxide
C．the increase in the amount of carbon dioxide will take place over many years
D．the carbon dioxide content of the atmosphere is decreasing

网考网参考答案：B
网考网解析：
推理题。由文章第一段结尾“The Americans have shown conclusively that the aerosol question is dominant.”和第二段末句“But the other problem now looms larger than ever.”以及上下文关于二氧化碳和浮质问题的比较，可知浮质问题更严重。A、C、D均与原文事实细节相悖。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>