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Air pollution is caused mainly by emissions from road vehicles, factories, power Stations, aircraft and the like and by the ‘large-scale burning of vegetation. It has long been recognized as an environmental problem, and as a source of costs to both industry and entire communities. Only relatively recently, however, has the full Significance of the impact of such pollution become apparent. and the global dominant, potentially disastrous, environmental problem facing humanity. Since the mid-eighteen century the burning of fossil fuels, deforestation, and other changes in land use have resulted in substantial increases in the concentration of carbon dioxide, ‘Methane, and nitrogen oxides in the atmosphere. By blocking the radiation back into space of much of the heat reaching the earth from the sun, these gases reduce Significantly the natural cooling - ‘effect of such radiation, thus creating a ‘greenhouse effect’ and causing a steady increase in temperatures on earth global warming. Although the Claim that: the earth’s atmosphere IS heating up has been dispute by some climatologists, the balance of scientific opinion is now firmly behind the hypothesis.

The principle focus of the passage Is wren

• A. ciimatechange
• B. ciimatechange
• C. ciimatechange
• D. ciimatechange

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