单项选择题

A．Inland seas.
B．Factories.
C．Drug companies.
D．Mountain streams.
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The use of solar and wind power is now increasing rapidly, raising hope that such alter-native energy technologies can significantly reduce greenhouse gas emissions and generate new jobs. The global wind power industry, for example, has become a $ 2-billion-a-year business, expanding at a rate of 25% per year. India, China, and a dozen European nations have installed thousands of wind turbines that generate electricity at a cost comparable to new coal-fired power plants. In the 1990s, Germany has created 10,000 new jobs in its wind industry. Wind power now provides less than 1% of the world’s total electricity, but that figure could climb to 20% or more within 50 years, according to Worldwatch Institute researchers. Solar power is the second fastest growing energy source today. The cost of buying a kilowatt worth of solar photovoltaic cells dropped from $ 70,000 in the 1970s to $ 4,000 in 1997, and in 10 years it could go as low as $1,000. Approximately 400,000 homes--many in remote areas not connected by power lines--already use solar power. Worldwatch studies suggest that covering the rooftops of existing buildings with solar cells could meet more than half of the electricity needs each year.
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