Câu hỏi:
21/03/2020 429Read 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 30 to 34.
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 change. 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 the more important air pollutants, such as sulfur oxides, carbon monoxide, 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 increased 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.
What does the passage mainly discuss?
Đáp án chính xác
Câu hỏi trong đề:
Tổng hợp đề luyện thi Đại Học môn Tiếng Anh có lời giải !!
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Trả lời:
Giải bởi Vietjack
Chọn B.
Đáp án là B.
Giải thích: Bài văn chủ yếu bàn về :
A. Tác động về mặt kinh tế của ô nhiễm không khí
B. Những gì hợp thành 1 tác nhân ô nhiễm không khí
C. Mức độ nguy hại mà chất ô nhiễm gây ra
D. Ảnh hưởng của các hợp chất bị thêm vào không khí
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 correct answer to 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 correct answer to each of the following questions.
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Câu 3:
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.
Tom went on and on apologizing for it, which was quite unnecessary.
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Câu 4:
Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
________, tell him I have gone to London.
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Câu 5:
Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.
It announced today that an enquiry would be held into the collapse of ahigh-rise apartment block
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Câu 6:
Mark the letter A, B, C, or D on your answer sheet to indicate the word whose underlined part differs from the other three in pronunciation in 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 word that differs from the other three in the position of primary stress in each of the following questions.
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