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 55 to 64.

      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 inEngland 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? 

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The next meeting _________ in May.

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The librarian told us not _________ reference books out of the library.

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__________ candidates are likely to succeed in job interviews. 

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In Vietnam, two or more ________ may live in a home. 

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A good essay must __________contain enough interesting ideas and specific exam but also have good organization

Mark the letter A, B, C, or D on your answer sheet to indicate the word or phrase that is CLOSEST in meaning to the underlined part in each of the following questions from 25 to 29.

Today’s scientists have overcome many of the challenges of the depth by using more sophisticated tools.

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Each year about fifty hundred species of plants and animals are already being eliminated.

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I just can't ______ that noise any longer!

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It’s(A) not that I don’t like her, but I object (B) to be called (C) that by her. I am  not her“buddy”, (D) am I?

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The ground is wet. It ________ rained last night.

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______ should a young child be allowed to play with fireworks without adult supervision

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_________ migrate long distances is well documented.

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The boy was sent to the police because of several ________ that he had taken part in.

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I can^’t sleep ________ the hot weather.

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John: "Congratulations! You did great.                      Mary:  - " ___________.”