Câu hỏi:
29/03/2020 188Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions from 43 to 50.
An air pollutant is defined as a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetation, or materials adversely. Air pollution requires a very flexible definition that permits continuous changes. When the first air pollution laws were established in England in the fourteenth century, air pollutants were limited to compounds that could be seen or smelled - a far cry from the extensive list of harmful substances known today. As technology has developed and knowledge of the health aspects of various chemicals has increased, the list of air pollutants has lengthened. In the future, even water vapor might be considered an air pollutant under certain conditions.
Many of more important air pollutants, such as sulfur oxides, carbon monoxides and nitrogen oxides are found in nature. As the Earth developed, the concentration of these pollutants was altered by various chemical reactions; they became components in biogeochemical cycles. These 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 that resulting from human activities.
However, human production usually occurs in a localized area, such as a city. In such a region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is an concentration of noxious chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact, the numerical value 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 (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.
What does the passage mainly dicuss?
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Trả lời:
Giải bởi Vietjack
Kiến thức: Đọc hiểu
Giải thích:
Đoạn văn chủ yếu bàn luận về điều gì?
A. Điều gì tạo thành một chất gây ô nhiễm không khí.
B. Có bao nhiêu tác hại gây ô nhiễm không khí có thể gây ra.
C. Tác động kinh tế của ô nhiễm không khí.
|D. Tác động của các hợp chất được thêm vào khí quyển
Đáp án: A
Nhà sách VIETJACK:
CÂU HỎI HOT CÙNG CHỦ ĐỀ
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Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions.
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Câu 2:
Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.
“Shall I carry the suitcase for you, Mary?”, said John.
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Câu 3:
Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions.
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Câu 4:
Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the underlined word(s) in each of the following questions.
In my attempt to win a place at university, I am under a lot of pressure.
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Câu 5:
Mark the letter A, B, C, or D on your answer sheet to indicate the most suitable response to complete each of the following exchanges.
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John: “ __________________. ”
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Câu 6:
Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
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Câu 7:
Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
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