問題詳情

Question 40-50Scientists have discovered that for the last 160,000 years, at least, there hasbeen a consistent relationship between the amount of carbon dioxide in the air andthe average temperature of the planet. The importance of carbon dioxide inregulating the Earth's temperature was confirmed by scientists working in eastern(5) Antarctica. Drilling down into a glacier, they extracted a mile-long cylinder of icefrom the hole. The glacier had formed as layer upon layer of snow accumulated yearafter year. Thus drilling into the ice was tantamount to drilling back through time.The deepest sections of the core are composed of water that fell as snow160,000 years ago. Scientists in Grenoble, France, fractured portions of the core and(10)measured the composition of ancient air released from bubbles in the ice.Instruments were used to measure the ratio of certain isotopes in the frozen water toget an idea of the prevailing atmospheric temperature at the time when thatparticular bit of water became locked in the glacier.The result is a remarkable unbroken record of temperature and of atmospheric(15)levels of carbon dioxide. Almost every time the chill of an ice age descended on theplanet, carbon dioxide levels dropped. When the global temperature dropped 9°F (5 °C),carbon dioxide levels dropped to 190 parts per million or so. Generally, as eachice age ended and the Earth basked in a warm interglacial period, carbon dioxidelevels were around 280 parts per million. Through the 160,000 years of that ice(20)record, the level of carbon dioxide in the atmosphere fluctuated between 190 and280 parts per million, but never rose much higher-until the Industrial Revolutionbeginning in the eighteenth century and continuing today.There is indirect evidence that the link between carbon dioxide levels andglobal temperature change goes back much further than the glacial record. Carbon(25) dioxide levels may have been much greater than the current concentration during theCarboniferous period, 360 to 285 million years ago. The period was named for aprofusion of plant life whose buried remains produced a large fraction of the coaldeposits that are being brought to the surface and burned today.
40. Which of the following does the passage mainly discuss?
(A) Chemical causes of ice ages
(B) Techniques for studying ancient layers of ice in glaciers
(C) Evidence of a relationship between levels of carbon dioxide and global temperature
(D) Effects of plant life on carbon dioxide levels in the atmosphere

參考答案

答案：C
難度：適中0.666667
統計：A(0),B(0),C(2),D(1),E(0)

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