题目内容
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Over the past decades, sea ice ______ in the Arctic (北极) as a result of global warming.
A．had decreased
B．will decrease
C．has been decreasing
D．is decreasing
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A、£1.40
B、£3.40
C、£2.40
D、0
A、inform
B、infomred
C、informing
D、to inform
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 (北极的) 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 the lead sources. The dominant lead ratio found in Greenland snow matched that found ingasoline from the United States.
In a study published in the journal Ambio, scientists found that 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 respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.
The study published in the journal Nature indicates that
A．the Clean Air Act has not produced the desired results.
B．lead deposits in arctic snow on the increase.
C．lead will stay in soil and snow longer than expected.
D．the U.S. is the major source of lead pollution in arctic snow.
A. all the time B. in any circumstances C. in a growing market D. in a shrinking market
A. mistakes are not important in the process of learning a language B. learners are often very afraid of making mistakes C. making mistakes can help the learner discover the rules of the language D. native speakers often do not tell foreign language learners about their mistake
A. the development of the society B. the explosion of information C. The need for specialists D. the civilization of human beings
A. of B. with C. out D. on
A. that B. whose C. in which D. of which
A./; / B. the; the C./; the D. the; /
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