考研考试

【单选题】ThatArctic sea ice is disappearing has been known for decades. The underlying cause is believed by all but a handful of climatologists to be global warming brought about by greenhouse-gas emissions. Yet the rate the ice is vanishing confuses these climatologists’ models. These predict that if the level of carbon dioxide, methane and so on in the atmosphere continues to rise, then theArctic Ocean will be free of floating summer ice by the end of the century.At current rates of shrinkage, by contrast, this looks likely to happen sometime between 2020 and 2050.
The reason is thatArctic air is warming twice as fast as the atmosphere as a whole. Some of the causes of this are understood, but some are not. The darkness of land and water compared with the reflectiveness of snow and ice means that when the latter melt to reveal the former, the area exposed absorbs more heat from the sun and reflects less of it back into space. The result is a feedback loop that accelerates local warming. Such feedback, though, does not completely explain what is happening. Hence the search for other things that might assist the ice’s rapid disappearance.
One is physical change in the ice itself. Formerly a solid mass that melted and refroze at its edges, it is now thinner, more fractured, and so more liable to melt.But that is (literally and figuratively) a marginal effect. Filling the gap between model and reality may need something besides this. The latest candidates are "short-term climate forcings". These are pollutants, particularly ozone and soot (also called "black carbon") that do not hang around in the atmosphere as carbon dioxide does, but have to be renewed continually if they are to have a lasting effect. If they are so renewed, though, their impact may be as big asCO₂’s.
Reducing soot would not stop the summer sea ice disappearing, but it might delay the process by a decade or two.According to a recent report by the United NationsEnvironment Program, reducing soot and ozone in the lower part of the atmosphere, especially in theArctic countries ofAmerica,Canada, Russia and Scandinavia, could cut warming in theArctic by two-thirds over the next three decades. Indeed, the report suggests, if such measures—preventing crop burning and forest fires, cleaning up diesel engines and wood stoves, and so on—were adopted everywhere they could halve the wider rate of wanning by 2050.
The rapid melting of theArctic sea ice, then, illuminates the difficulty of modeling the climate—but not in a way that brings much comfort to those who hope that fears about the future climate might prove exaggerateD、When reality is changing faster than theory suggests it should, a certain amount of nervousness is a reasonable response.
Which of the following is true of the reasons mentioned in Paragraph 3

A、The physical change happened to ice makes it easier to melt.
B、The physical change of ice is the leading cause ofArctic ice melting.

C、The pollutants like ozone and soot are not as influential asCO2.
D、Ozone and soot can exert an effect as long-lasting asCO2 does.
网考网参考答案：A
网考网解析：
[解析] 细节题。根据题干定位到第三段。该段第一句话承接第二段，指出北极海冰迅速消融的另一个原因，即冰体本身的物理变化(physical change in the ice itself)。第二句话指出先前冰体巨大而坚固，只是在其边缘部分发生融化和再次冻结，现在冰层变薄变脆，因此更容易融化(now thinner, more fractured, and so more liable to melt)，故A项符合文意，为正确答案。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>