Read the following passage and mark the letter A, B, C, or D on your answer sheet to each of the questions
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 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 sulphur oxides, carbon monoxide, and nitrogen oxides, are found in nature. As the Earth developed, the concentrations of these pollutants were altered by various chemical reactions; they became components in biogeochemical cycle. 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 this localized regions, human output may be dominant and may temporarily overload the natural purification scheme of the cycle. 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. For example, sulphur dioxide has detectable health effects at 0.08 parts per million (ppm), which is about 400 times its natural level. Carbon monoxide, however, as a natural level of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm.
Question: It can be inferred from the first paragraph that ___________.
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A.
water vapor is an air pollutant in localized areas
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B.
most air pollutants today can be seen or smelled
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C.
the definition of air pollution will continue to change
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D.
a substance becomes an air pollutant only in cities
Đoạn 1: 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 health aspects of various chemicals has increased, the list of air pollutants has lengthened.
Tạm dịch: Chất gây ô nhiễm không khí được định nghĩa là hợp chất do con người trực tiếp hoặc gián tiếp đưa vào khí quyển với số lượng có thể ảnh hưởng xấu đến con người, động vật, thảm thực vật hoặc vật liệu. Ô nhiễm không khí đòi hỏi một định nghĩa rất linh hoạt cho phép thay đổi liên tục. Khi luật ô nhiễm không khí đầu tiên được ban hành ở Anh vào thế kỷ XIV, chất gây ô nhiễm không khí chỉ giới hạn ở những hợp chất có thể nhìn thấy hoặc ngửi thấy - rất khác so với danh sách dài các chất có hại được biết đến ngày nay. Khi công nghệ phát triển và kiến thức về các khía cạnh sức khỏe của nhiều loại hóa chất tăng lên, danh sách các chất gây ô nhiễm không khí cũng dài ra.)
Có thể suy ra từ đoạn văn đầu tiên rằng ___________.
A. hơi nước là chất gây ô nhiễm không khí ở những khu vực cục bộ
B. hầu hết các chất gây ô nhiễm không khí hiện nay đều có thể nhìn thấy hoặc ngửi thấy
C. định nghĩa về ô nhiễm không khí sẽ tiếp tục thay đổi
D. một chất chỉ trở thành chất gây ô nhiễm không khí ở các thành phố
Chọn C
Đáp án : C
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