Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北極的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (區(qū)分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生態(tài)系統(tǒng)) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.

Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北極的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (區(qū)分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生態(tài)系統(tǒng)) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.

Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北極的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (區(qū)分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生態(tài)系統(tǒng)) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.

Questions 16 to 20 are based on the following passage.
In a time of low academic achievement by children in the United States, many Americans are turning to Japan, a country of high academic achievement and economic success, for possible answers. However, the answers provided by Japanese preschools are not the ones Americans expected to find. In most Japanese preschools, surprisingly little emphasis is put on academic instruction. In one investigation, 300 Japanese and 210 American preschool teachers, child development specialists, and parents were asked about various aspects of early childhood education. Only 2 percent of the Japanese respondents (答問(wèn)卷者) listed “to give children a good start academically” as one of their top three reasons for a society to have preschools. In contrast, over half the American respondents chose this as one of their top three choices. To prepare children for successful careers in first grade and beyond, Japanese schools do not teach reading, writing, and mathematics, but rather skills such as persistence, concentration, and the ability to function as a member of a group. The vast majority of young Japanese children are taught to read at home by their parents.
In the recent comparison of Japanese and American preschool education, 91 percent of Japanese respondents chose providing children with a group experience as one of their top three reasons for a society to have preschools. Sixty-two percent of the more individually oriented (強(qiáng)調(diào)個(gè)性發(fā)展的) Americans listed group experience as one of their top three choices. An emphasis on the importance of the group seen in Japanese early childhood education continues into elementary school education.
Like in America, there is diversity in Japanese early childhood education. Some Japanese kindergartens have specific aims, such as early musical training or potential development. In large cities, some kindergartens are attached to universities that have elementary and secondary schools. Some Japanese parents believe that if their young children attend a university-based program, it will increase the children’s chances of eventually being admitted to top-rated schools and universities. Several more progressive programs have introduced free play as a way out for the heavy intellectualizing in some Japanese kindergartens.

Questions 16 to 20 are based on the following passage.
In a time of low academic achievement by children in the United States, many Americans are turning to Japan, a country of high academic achievement and economic success, for possible answers. However, the answers provided by Japanese preschools are not the ones Americans expected to find. In most Japanese preschools, surprisingly little emphasis is put on academic instruction. In one investigation, 300 Japanese and 210 American preschool teachers, child development specialists, and parents were asked about various aspects of early childhood education. Only 2 percent of the Japanese respondents (答問(wèn)卷者) listed “to give children a good start academically” as one of their top three reasons for a society to have preschools. In contrast, over half the American respondents chose this as one of their top three choices. To prepare children for successful careers in first grade and beyond, Japanese schools do not teach reading, writing, and mathematics, but rather skills such as persistence, concentration, and the ability to function as a member of a group. The vast majority of young Japanese children are taught to read at home by their parents.
In the recent comparison of Japanese and American preschool education, 91 percent of Japanese respondents chose providing children with a group experience as one of their top three reasons for a society to have preschools. Sixty-two percent of the more individually oriented (強(qiáng)調(diào)個(gè)性發(fā)展的) Americans listed group experience as one of their top three choices. An emphasis on the importance of the group seen in Japanese early childhood education continues into elementary school education.
Like in America, there is diversity in Japanese early childhood education. Some Japanese kindergartens have specific aims, such as early musical training or potential development. In large cities, some kindergartens are attached to universities that have elementary and secondary schools. Some Japanese parents believe that if their young children attend a university-based program, it will increase the children’s chances of eventually being admitted to top-rated schools and universities. Several more progressive programs have introduced free play as a way out for the heavy intellectualizing in some Japanese kindergartens.