Question

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 43 to 50.

        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 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 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 a region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is an 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.

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

A. will react harmfully with natural pollutants. 

B. can overwhelm the natural system removing pollutants. 

C. will damage area outside of the localized regions. 

D. can be dwarfed by nature's output of pollutants.

Answer 1

Kiến thức: Đọc hiểu

Giải thích:

Theo đoạn văn, ô nhiễm không khí do con người tạo ra ở các vùng địa phương _______.

A. sẽ phản ứng vô hại với các chất gây ô nhiễm tự nhiên.

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

C. sẽ làm hỏng khu vực bên ngoài các khu vực địa phương hóa.

D. có thể bị lấn át bởi sản lượng của các chất gây ô nhiễm.

Dẫn chứng: 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. Tạm dịch: Tuy nhiên, sản xuất của con người thường xảy ra ở một khu vực địa phương, chẳng hạn như một thành phố. Trong một khu vực như vậy, sản lượng của con người có thể chiếm ưu thế và có thể tạm thời quá tải kế hoạch thanh lọc tự nhiên của các chu kỳ.

Đáp án: B