The demand for energy is certain to increase...as an ever larger population strives to improve its standard of living. Petroleum

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问题    The demand for energy is certain to increase...as an ever larger population strives to improve its standard of living. Petroleum, natural gas, hydroelectricity, supply networks, new renewable energy technology, nuclear energy and more... Managing the energy challenge each country faces is very complex nowadays and will be decisive for the future.

   The future for petroleum use at the moment looks rather uncertain, despite enjoying the major benefit of a very advanced infrastructure already in place. The downsides from the environmental point of view are patently obvious: harm to public health through carbon dioxide emissions in exhaust fumes.
   The picture for natural gas is similarly mixed. While its main strength lies in its being a relatively clean fuel involving little processing and being easily transportable via pipelines, natural gas requires compression or low temperatures if it is to be used for cars or other vehicles.
   Yet there is another problem with natural gas. It may produce less carbon dioxide than other fossil fuels, but the major stumbling block to its use is that the methane released lives for a long time in the atmosphere. In addition, as it is a no-renewable energy source like petroleum, in coming years natural gas will not be in use. But in the short term at least, the situation looks rosy.
   Ethanol, the production from grain is relatively straightforward. It is made from harvested crops. As the demand for alternative ’clean’ fuels increases, farmers are switching from planting crops for consumption to fuel crops like corn, barley, wheat or others that produce oil like palm and rape seed. Despite the drawback of a shortage of commercial outlets, ethanol heralds a new dawn for the energy market. But, before we consider ethanol in depth, let’ s look at hydrogen. It is perhaps the most attractive of all renewable fuels. Its greatest appeal is that it is readily available everywhere in the form of water. Solar energy is used to split the water into hydrogen and oxygen and then recombine it, with water being the waste by-product. Perhaps its main drawback is making the hydrogen production units small enough to fit cars. But once this happens, the future of hydrogen is bright indeed.
   We are facing a real urgency with the climate crisis aroused by burning fossil fuels like coal and oil for energy. Many scientists say we need to lower CO2 level by sixty percent over the next forty years. If we don’ t, there could be terrible consequences for the environment and the world economy. Though governments are talking about ways to lower pollution levels, they may not be enough. By going carbon neutral, people and businesses can really do something to meet this global challenge.
Questions 56 ~ 60
Complete the following schema with no more than three words according to the passage.


选项

答案methane

解析 文章第四段第二句提到“天然气可能比其他化石燃料产生更少的二氧化碳,但其使用的主要障碍是释放的甲烷在大气中存在很长时间”。因此,空格处应填methane。
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