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.

A is the correct option.

Explanation:

It was officially declared eradicated in 1979 in the United States.

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.

i think it would be 5