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Coal is expected to continue to account for almost 27 percent of the world’s energy needs. With growing international awareness

admin2012-10-20  91
问题      Coal is expected to continue to account for almost 27 percent of the world’s energy needs. With growing international awareness of pressures on the environment and the need to achieve sustainable development of energy resources, a wide range of pollution control practices is in place at most modem mines. In addition, major research and development programmers are being devoted to lifting efficiencies and reducing emissions of greenhouse gases during coal consumption. Such measures are helping coal to maintain its status as a major supplier of the world’s energy needs.
     The coal industry has been targeted by its critics as a significant contributor to the greenhouse effect. However, the greenhouse effect is a natural phenomenon involving the increase in global surface temperature due to the presence of greenhouse gases—water vapor, carbon dioxide, methane and nitrous oxide--in the atmosphere. Without the greenhouse effect, the earth’s average surface temperature would be 33-35℃ lower, or -15℃. Life on earth, as we know it today, would not be possible.
     There is concern that this natural phenomenon is being altered by a greater build-up of gases from human activity, perhaps giving rise to additional warming and changes in the earth’ s climate. This additional build-up and its forecast outcome has been called the enhanced greenhouse effect. Considerable uncertainty exists, however, about the enhanced greenhouse effect, particularly in relation to the extent and timing of any future increases in global temperature.
     Greenhouse gases arise from a wide range of sources and their increasing concentration is largely related to the compound effects of increased population, improved living standards and changes in lifestyle. From a current base of 5 billion, the United Nations predicts that the global population may stabilize in the twenty-first century between 8 and 14 billion, with more than 90 percent of the projected increase taking place in the
world’s developing nations. The associated activities to support that growth, particularly to produce the required energy and food, will cause further increases in greenhouse gas emissions. The challenge, therefore, is to attain a sustainable balance between population, economic growth and the environment.
     The major greenhouse gas emissions from human activities are carbon dioxide (CO2), methane and njtrous oxide. Chlorofiuorocarbons (CFCs) are the only major contributor to the greenhouse effect that does not occur naturally, coming from such sources as refrigeration, plastics and manufacture. Coal’s total contribution to greenhouse gas emissions is thought to be about 18 percent, with about half of this coming from electricity generation.  
What is true about the greenhouse effect?
选项 A、It is caused by human activity.
B、It creates greenhouse gases such as carbon dioxide.
C、It prevents the earth’s surface temperature from becoming lower.
D、It does harm to life on earth.
答案C
解析 细节理解题。对应原文第二段:Without the greenhouse effect, the earth’s average surface tempera7 ture would be 33-35℃ lower, or-15℃. 答案为C。
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