Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from...

LQ

Lê Quỳnh Anh

21 tháng 5 2019

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 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...

Đọc tiếp

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 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?

A. The economic impact of air pollution.

B. What constitutes an air pollutant.

C. How much harm air pollutants can cause.

D. The effects of compounds added to the atmosphere.

#Mẫu giáo

1

DH

Dương Hoàn Anh

21 tháng 5 2019

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

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LQ

Lê Quỳnh Anh

2 tháng 7 2018

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50. A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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,...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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 concentrations of these pollutants were 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 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 littleuntil we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfurdioxide 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 47: Natural pollutants can play an important role in controlling air pollution for which of the following reasons?

A. They function as part of a purification process.

B. They occur in greater quantities than other pollutants.

C. They are less harmful to living beings than are other pollutants.

D. They have existed since the Earth developed.

#Mẫu giáo

1

DH

Dương Hoàn Anh

2 tháng 7 2018

Đáp án A

Dịch nghĩa: Những chất ô nhiễm tự nhiên có thể đóng vai trò quan trọng trong việc kiểm soát ô nhiễm không khí vì sao?

A. Chúng hoạt động như một phần của quá trình làm sạch.

B. Chúng xuất hiện với số lượng lớn hơn rất nhiều so với các chất gây ô nhiễm khác.

C. Chúng ít có hại hơn đến những vật thể sống so với các chất ô nhiễm khác.

D. Chúng đã tồn tại từ khi Trái đất phát triển.

Giải thích: Thông tin ở đoạn cuối “In this localized regions, human output may be dominant and may temporarily overload the natural puriﬁcation scheme of the cycle.”

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LQ

Lê Quỳnh Anh

14 tháng 2 2017

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50. A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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,...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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 concentrations of these pollutants were 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 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 littleuntil we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfurdioxide 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 48: According to the passage, which of the following is true about human-generated air pollution in localized regions?

A. It can be dwarfed by nature's output of pollutants in the localized region.

B. It can overwhelm the natural system that removes pollutants.

C. It will damage areas outside of the localized regions.

D. It will react harmfully with naturally occurring pollutants.

#Mẫu giáo

1

DH

Dương Hoàn Anh

14 tháng 2 2017

Đáp án B

Dịch nghĩa: Theo như đoạn văn, trong số những câu sau, đâu là câu đúng khi nói về ô nhiễm không khí do con người tạo ra ở những vùng địa phương?

A. Nó có thể bị hạn chế những chất thải tự nhiên của chất gây ô nhiễm môi trường tại vùng địa phương

B. Nó có thể áp đảo hệ thống tự nhiên mà loại bỏ những chất gây ô nhiễm.

C. Nó sẽ làm hư hại những khu vực phía ngoài vùng địa phương.

D. Nó sẽ phản ứng gây hại cùng với những chất gây ô nhiễm tự nhiên khác.

Giải thích: Thông tin ở “The concentrations at which the adverse eﬁects appear will be greater than the concentrations that the pollutants would have in the absence of human activities”

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LQ

Lê Quỳnh Anh

22 tháng 2 2019

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50. A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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,...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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 concentrations of these pollutants were 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 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 littleuntil we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfurdioxide 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 50: Which of the following is best supported by the passage?

A. To effectively control pollution local government should regularly review their air pollution laws.

B. One of the most important steps in preserving natural lands is to better enforce air pollution laws.

C. Scientists should be consulted in order to establish uniform limits for all air pollutants.

D. Human activities have been effective in reducing air pollution.

#Mẫu giáo

1

DH

Dương Hoàn Anh

22 tháng 2 2019

Đáp án A

Dịch nghĩa: Trong số những câu sau, câu nào đúng nhất, theo đoạn văn?

A. Để có thể kiểm soát hiệu quả ô nhiễm, chính quyền địa phương cần thường xuyên xem xét lại luật về ô nhiễm không khí.

B. Một trong những bước quan trọng nhất để bảo tồn đất đai thiên nhiên là áp dụng tốt hơn luật lệ về ô nhiễm không khí.

C. Nên tham khảo các nhà khoa học để có thể đề ra giới hạn chung về chất gây ô nhiễm không khí.

D. Hoạt động của con người rất có hiệu quả trong việc giảm thiểu ô nhiễm không khí.

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LQ

Lê Quỳnh Anh

1 tháng 8 2017

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 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...

Đọc tiếp

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 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.

According to the passage, human-generated air pollution in localized regions ___.

A. can be dwarfed by nature’s output of pollutants

B. can overwhelm the natural system that removes pollutants

C. will damage areas outside of the localized regions

D. will react harmfully with natural pollutants

#Mẫu giáo

1

DH

Dương Hoàn Anh

1 tháng 8 2017

Chọn B.

Đáp án là B.

Giải thích:

Đoạn 3: 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.

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LQ

Lê Quỳnh Anh

21 tháng 6 2017

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 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...

Đọc tiếp

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 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.

The word "adversely" in the first paragraph is closest in meaning to _______.

A. negatively

B. quickly

C. admittedly

D. considerably

#Mẫu giáo

1

DH

Dương Hoàn Anh

21 tháng 6 2017

Chọn A.

Đáp án là A.

Giải thích: Từ “adversely: 1 cách tiêu cực/bất lợi” gần nghĩa nhất với từ nào sau đây?

A. negatively: tiêu cực

B. quickly: nhanh chóng

C. admittedly: thừa nhận rằng

D. considerably: đáng kể

Dịch: 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.

(Một chất gây ô nhiễm không khí được định nghĩa là một hợp chất được đem trực tiếp hoặc gián tiếp vào khí quyển bởi con người ở một khối lượng gây ảnh hưởng đến con người, động vật, thực vật hay các nguyên liệu khác một cách tiêu cực.)

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LQ

Lê Quỳnh Anh

8 tháng 3 2017

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50. A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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,...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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 concentrations of these pollutants were 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 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 littleuntil we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfurdioxide 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 44: The word "adversely" is closest in meaning to ____________.

A. negatively

B. quickly

C. admittedly

D. considerably

#Mẫu giáo

1

DH

Dương Hoàn Anh

8 tháng 3 2017

Đáp án A

Dịch nghĩa: Từ “adversely” - tiêu cực, gần nghĩa nhất với _________.

A. tiêu cực B. nhanh chóng

C. rõ ràng là, phải thừa nhận là D. đáng kể

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LQ

Lê Quỳnh Anh

10 tháng 9 2019

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50. A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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,...

Đọc tiếp

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetaions, 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 concentrations of these pollutants were 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 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 littleuntil we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfurdioxide 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 45: It can be inferred from the first paragraph that _________.

A water vapor is an air pollutant in localized areas

B. most air pollutants today can be seen or smelled

C. the definition of air pollution will continue to change

D. a substance becomes an air pollutant only in cities

#Mẫu giáo

1

DH

Dương Hoàn Anh

10 tháng 9 2019

Đáp án C

Dịch nghĩa: Có thể suy ra từ đoạn đầu tiên là _________.

A. hơi nước là chất gây ô nhiễm không khí ở một số địa phương.

B. phần lớn các chất gây ô nhiễm không khí hiện nay đều có thể nhìn thấy hoặc ngửi thấy.

C. định nghĩa về chất gây ô nhiễm không khí sẽ tiếp tục thay đổi.

D. một chất trở thành chất gây ô nhiễm chỉ ở thành phố.

Giải thích: Đoạn 1 nói về các chất ô nhiễm không khí đã thay đổi từ quá khứ đến hiện tại, dự đoán thay đổi ở tương lai, như vậy đáp án C là chuẩn nhất.

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LQ

Lê Quỳnh Anh

6 tháng 9 2019

Read the following passage and choose the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions from 33 to 42. A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetations, or materials adversely. Air pollution requires a very flexible definition that permits continuous change. When the first air pollution laws were established in England...

Đọc tiếp

Read the following passage and choose the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions from 33 to 42.

A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetations, 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 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 form 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, 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.

Natural pollutants can play an important role in controlling air pollution for which of the following reasons?

A. They function as part of a purification process.

B. They occur in greater quantities than other pollutants.

C. They are less harmful to living beings than are other pollutants.

D. They have existed since the Earth developed.

#Mẫu giáo

1

DH

Dương Hoàn Anh

6 tháng 9 2019

Chọn A

Dòng 4 đoạn 2 “These serve as an air purification scheme”: chúng phục vụ như 1 kết hợp làm sạch-> quá trình làm sạch.

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