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  3. Planes may account for only 2 per cent of the world’s carbon emissions, but it is a figure destined to rise. The aviation indust

Planes may account for only 2 per cent of the world’s carbon emissions, but it is a figure destined to rise. The aviation indust

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问题     Planes may account for only 2 per cent of the world’s carbon emissions, but it is a figure destined to rise. The aviation industry is expanding at a dramatic rate, around 5% a year. Twice as many passengers are likely to be passing through British airports in 2020 compared with today, and three times by 2030.
    As the developed world acknowledges climate change warnings, the carbon emissions from other industries will fall. The aviation industry’s output will therefore account for an even larger percentage of emissions. One calculation, by the Climate Change Research(CCR), suggests the U. K. aviation industry could end up accounting for every gram of our carbon quota by 2040. Such calculations suppose aircraft designers cannot clean up their act, a suggestion firmly rejected by experts who point to a massive research program aimed at cutting fuel use by planes by around 50% by 2020, a move that would also halve their carbon emissions.
    To reach that aim, a key factor will be lightweight composites, materials made of several components, including carbon fibers. These are as strong and flexible as metal but as light as plastic. Planes such as the Airbus A340 are already made of material that is 10 per cent carbon composite. This cuts weight, decreases fuel use and reduces carbon emissions. The next generation of aircrafts, will make even more use of composites: a tremendous saving in weight, fuel and carbon.
    Then there is the simple matter of air traffic control. At present, individual countries have their own routes for aircraft crossing their airspaces. "Essentially aircraft travel on doglegs across Europe, and that is very inefficient in terms of fuel use," said Dr. John Green, of the Royal Aeronautical Society. "We need to rationalize air traffic control so that planes fly in straight, energy-efficient lines, an idea that is now being discussed in the EU. "
    Finally, there is aviation fuel. Making it ecologically friendly poses the greatest challenges of all. Biofuels can be used as petrol and diesel substitutes for cars and lorries, but not in planes. "Biofuel is essentially alcohol, and that burns at the wrong temperature for aircraft engines," says Green. "We can use coal to make kerosene, which we could burn in aircraft engines, but that does not help the issue of global warming, of course. " But this does not stop scientists from dreaming. One idea, put forward by the U. S. geneticist Craig Venter last week, would be to create micro-organisms, fitted with artificial chromosomes, which could convert sunlight into fuels that could be burnt in aircraft. These would not involve burning fossil carbon and would be the perfect green fuel. It is still a far-off prospect but realistic, say biologists.
According to the text, what can we learn about aviation fuels?
选项 A、Biofuels can be used as replacement for vehicles as well as planes.
B、Neither biofuels nor coals can be used for planes.
C、The idea of green fuel is to change solar energy into fuels.
D、The idea of green-fuel, which is only an illusion, is challenged and doubted by scientists.
答案C
解析 根据本文，关于航空燃料我们可知：[A]生物燃料可作为汽车和飞机的燃料的替代品。[B]生物燃料和煤都不适用于飞机。[C]绿色燃料就是将太阳能转化成燃料。[D]绿色燃料只是一种幻想，受到了科学家们的挑战和质疑。根据题干关键词aviation fuels可以定位到第五段。[C]为第五段倒数第二句的同义转述，故为正确答案。根据该段第三句可知[A]不符合事实，biofuels的燃烧温度不适用于飞机引擎。从第五句可知飞机可以使用coal作为燃料，但是对于环保没有帮助，所以[B]也不符合文意。[D]中的illusion意为“幻想；错误的观念”，显然与最后一句话不符，所以可以排除。
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