【单选题】Lead deposits, which accumulated in soil and snow during the 1960's and 1970's, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Cl...
A.
lead deposits in arctic snow are on the increase
B.
the Clean Air Act has not produced the desired results
C.
the US is the major source of lead pollution in arctic snow
D.
lead will stay in soil and snow longer than expected