Câu hỏi: Read 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 23 to 29.
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 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 region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is a 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.
A. the various chemical reactions.
B. the compound moved to the water or soil.
C. the pollutants from the developing Earth.
D. the components in biogeochemical cycles.
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 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 region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is a 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.
Source: Adapted from Objective PET
The word "these" in paragraph 2 refers to ____________A. the various chemical reactions.
B. the compound moved to the water or soil.
C. the pollutants from the developing Earth.
D. the components in biogeochemical cycles.
Kiến thức: Đọc hiểu
Giải thích:
Từ "these" trong đoạn 2 đề cập đến ____________
A. các phản ứng hóa học khác nhau.
B. hợp chất di chuyển vào nước hoặc đất.
C. các chất ô nhiễm từ Trái đất đang phát triển.
D. các thành phần trong chu trình sinh địa hoá.
Thông tin: 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.
Tạm dịch: Khi Trái đất phát triển, nồng độ của các chất ô nhiễm này bị thay đổi bởi các phản ứng hóa học khác nhau, chúng trở thành thành phần trong các chu trình sinh địa hóa. Chúng phục vụ như một sơ đồ lọc không khí bằng cách cho phép các hợp chất di chuyển từ không khí sang nước hoặc đất.
Giải thích:
Từ "these" trong đoạn 2 đề cập đến ____________
A. các phản ứng hóa học khác nhau.
B. hợp chất di chuyển vào nước hoặc đất.
C. các chất ô nhiễm từ Trái đất đang phát triển.
D. các thành phần trong chu trình sinh địa hoá.
Thông tin: 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.
Tạm dịch: Khi Trái đất phát triển, nồng độ của các chất ô nhiễm này bị thay đổi bởi các phản ứng hóa học khác nhau, chúng trở thành thành phần trong các chu trình sinh địa hóa. Chúng phục vụ như một sơ đồ lọc không khí bằng cách cho phép các hợp chất di chuyển từ không khí sang nước hoặc đất.
Đáp án D.