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Narrator Listen to part of a talk in an environmental science class.
Narrator Listen to part of a talk in an environmental science class.
游客
2024-01-04
58
管理
问题
Narrator
Listen to part of a talk in an environmental science class.
Now get ready to answer the questions. You may use your notes to help you answer. [br] What may be influenced by air pollutants?
How much can you say about air pollutant? At first let’s have a look at a useful definition of it. A pollutant is a compound added directly or indirectly by humans to the atmosphere, and in such quantities to adversely affect humans, animals, vegetations or materials. On the other hand air pollution has a very flexible definition that allows continuous change. When the first air pollution law was established in England in the 14th century, air pollutants were limited to compounds that could be seen or smelled, which is very different from the list of harmful substances known today. As technology has developed and knowledge of health aspects has increased, the list of air pollutants has lengthened. In the future even water vapor might be thought of as an air pollutant under certain conditions.
Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides are found in nature. Perhaps in your daily life you can’t feel them clearly since they don’t make up a big percentage of the air. Before we have learnt something about the properties of the above substances, let’s have a look at their historical development. As the earth developed, the concentrations of these pollutants were altered by various chemical reactions and become biogeochemical components, and then they serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global basis, nature’s output of these compounds dwarfs those resulting from human activities. However, human production usually occurs in a localized area, such as a city.
In these localized regions, human output may be dominant and may temporarily overload the natural purification scheme of cycles. The result is an increased concentration of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact the concentration tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfur dioxide has detectable health effects at 0.08 parts per million, often shortened to ppm, which is about 400 times its natural level. Carbon monoxide, however, has a natural level of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm.
选项
A、Humans and animals.
B、The global climate.
C、Vegetations and plants.
D、Mineral materials.
答案
AC
解析
本题为篇章应用题的要点多选题,考生必须具备辨别什么是文中的主要观点,什么是次要观点,什么是事实和细节的能力。题目问:什么会受到空气污染物的影响?综合全文,受到空气污染物直接或间接影响的是人、动物、植物和原材料,因此选项A、C为正确答案,而选项B不是本文讨论的问题,选项D是矿物质,也与原文不符。
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