Explanation

(d) Hubble’s law is the statement in physical cosmology that the red shift in light coming from distant galaxies is proportional to their distance
$V = H_{0}D$
Where $V$ is the recessional velocity due o red shift, $H_{0}$ is Hubble’s constant, $D$ is the proper distance that the light had travelled from the galaxy in the res frame of the observer. This effect helps us in explaining the fact that galaxies are receding from us.