How do you find the ratio of perimeter and area?​

Given: circle a externally tangent to circle b. how many possible common tangents to circles a and b can exist? 2 3 4

Which revelation resulted from the observation of the spectrum of different galaxies? a. there were more galaxies whose spectrum was blueshifted b. there were no galaxies whose spectrum was redshifted c. there were more galaxies whose spectrum was redshifted d. there were no galaxies whose spectrum was blueshifted

What way does renewable energy differ from nonrenewable energy?