【单选题】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 Clea...
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.
【单选题】回答下列各题: Marriage emerged as the most popular institution throughout history primarily because it was an effective arrangement to improve the care and upbringing of children. Marriage is not necessary ...
A.
It is primarily a necessary step to have children.
B.
It meets resistance in Western and other rich countries.
C.
It has a tremendous impact on the rearing of children.
D.
It is the most important institution throughout history.