Note that the dilation converted the big square into the small one. This implies that the dilation was of "1/something" (for it dwarfed the original figure). Besides, note that the diagonal from cero to any vertex, for instance B, consists of the diagonal of six squares of the plane. However, the diagonal form cero to vertex B' consists of just three diagonals of the squares of the plane. This means that the dilation "divides" the size of the big square by three. The answer is A.