[单选题]
Substance A has a de arne,6wxxuo0a;wdl7r4 sim4 4 *ma7h:+ylsd 4ywfyf0mv92rv)k8*n jssm)gnsity 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
