雅思

　　飞机限制问题
　　2006-3-25 考题
　　Automobiles produce less pollution than do airplanes. Automobiles also consume less fossil fuel. Therefore it is necessary to restrict some flights. Do you agree or disagree with this opinion?
　　250 words
　　2006-3-25 北航
　　The argument that the flights should be restricted is invalid. Clearly, it is unconvincing to compare the volume of pollutants an airplane produces with that generated by an automobile, because an airplane is shared by many passengers while an automobile is usually for one or, at the best, several passengers.
　　Suppose a visitor drives 1,000 miles, burning 100 liter gasoline and emitting 10 cubic meter carbon dioxide, this very passenger is totally responsible for such an environment problem. But to what extent should another passenger, who travels the same distance by air, take environment responsibility? If the airplane consumes 10,000 liter gasoline and produces 1000 cubic meter carbon dioxide and if altogether 300 passengers share the flight, then traveling by air causes less environmental damage.
　　Another thing must also be in the list of consideration: the time. Traveling by air saves time. The point is that even if traveling by automobiles consumes less energy and produces less pollutants, traveling by air has a variety of reasons. For instance, a patient is transported by air from where she is injured to the hospital.
　　The opponents might argue that this is not the “unnecessary flights”. Nevertheless it is ambiguous and vague to use such a term. How to define an “unnecessary” flight? Is there a legal or generally accepted criterion against which the feature of a flight can be clearly and correctly labeled as “necessary” or “unnecessary”? Nay.
　　Therefore, the argument mentioned in the topic is neither logically sound nor practically significant.
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（责任编辑：中大编辑）