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10 tháng 6 2020

Câu hỏi của mai le - Tiếng anh lớp 8 | Học trực tuyến

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Read the passage and fill the blanks with the given w prediction anger deforestation processes decades Natural disasters result from natural (1)___________of the earth.However,in the last five decades,human activities have contributed to increasing the number of natural disasters.More landslides haveoccurred as a result of(2)_______________. Because there are fewertrees in the forest,the soil becomes loosends and more easily to be flushed down.Industrialization and...
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Read the passage and fill the blanks with the given w

prediction anger deforestation processes decades

Natural disasters result from natural (1)___________of the earth.However,in the last five decades,human activities have contributed to increasing the number of natural disasters.More landslides haveoccurred as a result of(2)_______________. Because there are fewertrees in the forest,the soil becomes loosends and more easily to be flushed down.Industrialization and urbanization contribute to global warming,leading to more intense disasters of all kinds,including hurricanes and tsunami.It is more difficult to have exact(3)____________of climate patterns such as ElNino and La Nina.According to the Office of US Foreign disaster Assistance,the total natural disasters reported each year have been steadily increasingin recent(4)_______________.In 1980,there were only about 100 hydro-meteorological disasters reported per year but that number has risen to over 300 a year since 2000.If humans do not take action,natural disasters will become more tragic ans we won't be able to cope with the(5)_____________of Mother Nature.

1
10 tháng 6 2020

Read the passage and fill the blanks with the given w

prediction anger deforestation processes decades

Natural disasters result from natural (1)______anger_____of the earth.However,in the last five decades,human activities have contributed to increasing the number of natural disasters.More landslides have occurred as a result of(2)_______deforestation________. Because there are fewertrees in the forest,the soil becomes loosends and more easily to be flushed down.Industrialization and urbanization contribute to global warming,leading to more intense disasters of all kinds,including hurricanes and tsunami.It is more difficult to have exact(3)______prediction______of climate patterns such as ElNino and La Nina.According to the Office of US Foreign disaster Assistance,the total natural disasters reported each year have been steadily increasingin recent(4)_______decades________.In 1980,there were only about 100 hydro-meteorological disasters reported per year but that number has risen to over 300 a year since 2000.If humans do not take action,natural disasters will become more tragic ans we won't be able to cope with the(5)______processes_______of Mother Nature

    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 subtances known...
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    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 subtances 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 notrigen 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 as 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 subtance to be a pollutant; in fact, the numerial value tells us little until we know how much of an increase this represents over ther 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.

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

A. They function as part of a purification process

B. They occur in greater quantities than oher pollutants

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

D. They have existed since the Earth developed

1
11 tháng 10 2017

Đáp án A.

Key words: natural pollutants, controlling air pollution, nature.

Câu hỏi: Dưới những lí do sau, đâu là lí do để chất gây ô nhiễm giữ vai trò quan trọng trong kiểm soát ô nhiễm không khí?

Clue: “Many of the more important air pollutants … are found in nature…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”: Nhiều trong số các chất ô nhiễm không khí … được tìm thấy trong tự nhiên …chúng trở thành thành phần trong chu trình sinh địa. Các chất này có vai trò như một kế hoạch thanh lọc không khí bằng cách cho phép hợp chất di chuyển từ không khí sang nước hoặc đất.

Phân tích: Từ Clue có thể tóm tắt lại là các chất gây ô nhiễm trong tự nhiên trở thành các chất hóa học khác, chất hóa học này lại tạo quy trình thanh lọc này. Chọn đáp án A. They function as part of a purification process.

Các đáp án khác:

          B. They occur in greater quantities than other pollutants: Các chất này hình thành với khối lượng lớn hơn các chất ô nhiễm khác – Không có thông tin.

          C. They are less harmful to living beings than other pollutants: Các chất này ít gây hại đến các sinh vật sống hơn các chất ô nhiễm khác – Không có thông tin.

          D. They have existed since the Earth developed: Chúng đã tồn tại kể từ khi Trái Đất hình thành – Không phải là một vai trò của ô nhiễm không khí.

    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 subtances known...
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    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 subtances 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 notrigen 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 as 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 subtance to be a pollutant; in fact, the numerial value tells us little until we know how much of an increase this represents over ther 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.

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

A. can be dawrfed 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

1
27 tháng 11 2017

Đáp án B.

Key words: human-generated, localized regions.

Câu hỏi: Theo bài khóa, đâu là ý đúng về các chất ô nhiễm không khí do con người gây ra ở các vùng chuyên môn hóa?

Clue: “In such a region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles”: Ở những vùng như vậy, chất thải của con người quá nhiều và có thể tạm thời quá tải áp đảo chương trình thanh lọc tự nhiên của chu trình.

Phân tích: Chu trình được nói đến ở trên là chu trình thanh lọc nhằm loại bỏ khí ô nhiễm. Do đó, ta chọn đáp án B. can overwhelm the natural system that removes pollutants: có thể áp đảo hệ thống tự nhiên loại bỏ các chất gây ô nhiễm. Các đáp án khác không phù hợp:

          A. can be dwarfed by nature’s output of pollutants: có thể bị làm ít đi bởi những chất gây ô nhiễm ngoài tự nhiên.

          C. will damage areas outside of the localized regions: sẽ gây hại khu vực bên ngoài một nơi nhất định.

          D. will react harmfully with natural pollutants: sẽ phản ứng gây hại đến những chất ô nhiễm tự nhiên.

    An air pollutnt 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 subtances known...
Đọc tiếp

    An air pollutnt 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 subtances 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 notrigen 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 as 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 subtance to be a pollutant; in fact, the numerial value tells us little until we know how much of an increase this represents over ther 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.

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 defiition of air pollution will continue to change

D. a subtance becomes an air pollutant only in cities

1
17 tháng 10 2017

Đáp án C.

Key words: inferred, first paragraph.

Câu hỏi: Có thể suy ra điều gì từ đoạn đầu tiên?

Clue: “Air pollution requires a very flexible definition that permits continuous change”: Ô nhiễm không khí đòi hỏi một định nghĩa linh hoạt cho phép sự thay đổi liên tục.

Phân tích: Dựa vào Clue ta thấy định nghĩa về ô nhiễm không khí do đó sẽ còn thay đổi. Chọn đáp án: C. the definition of air pollution will continue to change. Các đáp án khác không phù hợp:

          A. water vapor is an air pollutant in localized areas: hơi nước là ô nhiễm không khí ở các khu vực chuyên môn hóa.

          B. most air pollutants today can be seen or smelled: hầu hết ô nhiễm không khí ngày nay có thể nhìn được hoặc ngửi được.

          D. a substance becomes an air pollutant only in cities: một chất trở thành ô nhiễm không khí chỉ khi ở thành phố.

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,...
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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.

1
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.”

    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 subtances known...
Đọc tiếp

    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 subtances 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 notrigen 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 as 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 subtance to be a pollutant; in fact, the numerial value tells us little until we know how much of an increase this represents over ther 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.

According to the passage, the numerical value of the concentration level of a substance is only useful if ________.

A. the other substances in the area are known

B. it is in a localized area

C. the natural level is also known

D. it can be calculated quickly

1
25 tháng 12 2018

Đáp án C.

Key words: numerical value, concentration level.

Câu hỏi: Theo bài khóa, giá trị bằng con số của mức độ dồn lượng một chất sẽ chỉ hữu dụng khi nào?

Clue: “…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”

Phân tích: Ngay sau khi nhắc đến giá trị bằng con số, tác giả đưa ra ví dụ trong đó có sự xuất hiện của hai biến là “concentration level” và “natural level”. Do đó, để “concentration level” có ý nghĩa thì cũng phải biết “natural level”. Chọn đáp án C. the natural level is also known.

Các đáp án khác không phù hợp:

          A. the other substances in the area are known: các chất khác trong tự nhiên được biết.

          B. it is in a localized area: các chất có ở khu vực chuyên môn hóa.

          C. it can be calculated quickly: nó phải được tính nhanh.

    An air pollutnt 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 subtances known...
Đọc tiếp

    An air pollutnt 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 subtances 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 notrigen 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 as 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 subtance to be a pollutant; in fact, the numerial value tells us little until we know how much of an increase this represents over ther 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.

The word “adversely” in the first paragraph is closet in meaning to ________.

A. negatively        

B. quickly    

C. admittedly         

D. considerably

1
28 tháng 7 2017

Đáp án A.

Key words: paragraph 1, adversely

Clue: “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”: Ô nhiễm không khí được định nghĩa như hợp chất thải trực tiếp hoặc gián tiếp bởi con người vào không khí với một lượng để ảnh hưởng tiêu cực đến con người, động vật, thảm thực vật hoặc nguyên liệu.

adversely (adv) = in a way that is negative and unpleasant and not likely to produce a good result.

Vậy adversely gần nghĩa nhất với A. negatively: một cách tiêu cực.

Các đáp án còn lại là sai:

          B. quickly: nhanh chóng

          C. admittedly: được thừa nhận

          D. considerably: đáng kể

    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 subtances known...
Đọc tiếp

    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 subtances 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 notrigen 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 as 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 subtance to be a pollutant; in fact, the numerial value tells us little until we know how much of an increase this represents over ther 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.

The word “These” in the second paragraph is closet in meaning to ________.

A. the various chemical reactions

B. the pollutants from the developing Earth

C. the compounds moved to the water or soil

D. the components in biogeochemical cycles

1
29 tháng 1 2017

Đáp án D.

Key words: these, second paragraph, closet in meaning.

Clue: “…they became components in biogeochemical cycles. These serve as an air purification scheme by…”: … chúng trở thành thành phần trong chu trình sinh địa. Những chất này có vai trò như một chương trình thanh lọc không khí bằng cách …

Phân tích: “Chúng” ở đây là cụm danh từ được nhắc đến ngay trước đó. Vậy chọn đáp án D. the components in biogeochemical cycles.

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 following questions from 22 to 28.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...
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 following questions from 22 to 28.

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. 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

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

1
3 tháng 8 2017

Đáp án A

Đề: Vì lý do nào sau đây mà các chất gây ô nhiễm tự nhiên đóng vai trò quan trọng trong việc kiểm soát sự ô nhiễm không khí?

A. Chúng hoạt động với chức năng là một phần của quá trình thanh lọc.

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

C. Chúng ít có hại tới các sinh vật sống hơn so với các chất gây ô nhiễm khác.

D. Chúng đã luôn tồn tại từ khi trái đất hình thành.

Đoạn 2: “Many of the more important air pollutants, such as… 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…”

Dịch: Nhiều chất gây ô nhiễm không khí quan trọng/nghiêm trọng hơn, như… được tìm thấy trong tự nhiên. Khi trái đất hình thành/phát triển, chúng trở thành các thành phần trong các chu kỳ sinh hoá. Chúng có tác dụng như là một cách thanh lọc không khí…