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单项选择题

期货交易清算价即每个营业日的收盘前(  )秒或(  )秒内成交的所有交易的价格平均数。

A.30;60
B.30;90
C.45;60
D.45;90
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单项选择题
Polluting the Planet      
 
Garbage produced by people pollutes the planet. To help the planet recover, it helps to understand what effect pollution has on the environment.
      Buring fossil fuel is perhaps the greatest cause of pollution. But it is also the main means for making energy. The cheapest and surest way of providing electricity involves power plants that burn fossil fuels such as coal, which is transported to the plant using fuel also made from fossils. Burning fossil fuels causes much of the CO2 problem that contributes to climate change.
      A lot of the garbage that goes into landfill sites or is burned has to be treated first so that it doesn't send toxic chemicals into the land and the air. True, new landfills are carefully built so that these toxins don't escape, and the process of burning the garbage uses much cleaner technology than it used to. But all this requires energy, which is exactly what the world should use less of.
In developing countries, garbage may be dumped in any spare piece of land or in landfill sites that do nothing to protect the environment, or it may be burned without any thought for either nearby residents or the environment. This pollution causes health issues because it risks polluting the ground, local water sources, and the air.
Choose the correct answers.
Why are the new landfills better than the old ones?
A、They are treated first and then burned.
B、They are cleaned out regularly.
C、They don't require as much energy as the old ones did.
D、They protect the environment by not sending toxic chemicals into the ground.
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