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.

Answer: a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same sign as the  -4.0  µc charge.======electricstatic force between two point charges  is given by    where k is coulomb's constant,  8.99×10⁹  n·m²/c², q₁ and q₂ are the point charges, and r is the distance between the two point charges.assign positive to q₁let q₁ =  6.0 µc, q₂ = -4.0  µc, q₀ represent the charge at the origin, and q₃ represent this new charge to place.the charge at the origin q₀ would experience the following force f₀₁ from q₁, with r = 6.0 m (note that 1  µc = 10⁻⁶ c)    the force from q₂    the force from q₃    the net force on the origin charge, q₀, has to be zero for no electrostatic forcehaving an equation where k and q₀ can be divided out of the equation will allow us to solve for q₃    isolating:     a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same as the  -4.0  µc charge