Select the correct answer.
The chart gives the number of cases of polio between 1937 and 2011. Polio is an infectious disease that causes paralysis and sometimes death. The polio vaccine was introduced in 1955. What can be concluded about the polio vaccine?
a graph giving the number of cases of polio between 1937 and 2011 shows the polio vaccine introduced in 1955 and the number of polio cases tapering to zero through 2011
A.
It was successful in eradicating polio from the United States.
B.
It had no effect on the number of polio cases in the United States.
C.
It reduced the number of polio cases, but deaths from polio stayed constant.
D.
It initially lowered the number of polio cases, but the number of US cases remains high.
