Pls help it’s the middle question and it’s over geography

How would i answer this for an exam?

Which of these has the least impact on the climate of a place

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