单项选择题

A．shop stewards
B．agents
C．employees
D．trade officials
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energetic alert stimulated
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The climate phenomenon that is being blamed for floods, hurricanes and early snow- storms deserves credit for invigorating plants and helping to control the pollutant linked to global warming, a new study shows. El Nino---the periodic warming of eastern Pacific Ocean waters--causes a burst of plant growth throughout the world, and this removes carbon dioxide from the atmosphere, researchers have found. Natural weather events, such as the brief warming caused by El Nino, have a much more dramatic effect than previously believed on how much carbon dioxide is absorbed by plants and how much of the gas is expelled by the soils, said David Schimel of the National Center for Atmospheric Research. He is co-author of a study to be published in the journal Science. Atmospheric carbon dioxide, or C02, has been increasing steadily for decades. This is thought to be caused by an expanded use of fossil fuels and by toppling of tropical forests. Scientists have linked the CO2 rise to global warming, a phenomenon known as the green- house effect. Nations of the world now are drawing up plans to reduce fossil-fuel burning in hopes of reducing greenhouse gases in the atmosphere.
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