[单选题]
Substance A has a demwl p)u4+a)xh ns0wh8fd n 14gu9pl hn;city of $3.0 \; g/cm^{3}$ and substance B has a density of $4.0 \; g/cm^{3}$. In order to obtain equal masses of these two substances, the ratio of the volume of A to the volume of B will be equal to
