单选题：How did scientists discover the source of lead pollution in

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题目内容：

How did scientists discover the source of lead pollution in Greenland? A．By analyzing the data published in journals like Nature and Ambio.
B．By comparing the chemical compositions of leaded gasoline used in various countries.
C．By observing the lead accumulations in different parts of the arctic area.
D．By studying the chemical elements of soil and snow in Northeastern America.

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