Final answer:
The mass of a solid with variable density depends on the volume of the solid.
Step-by-step explanation:
The mass of a solid with variable density depends on the volume of the solid. Density is defined as the ratio of the mass of an object to its volume. Therefore, if the density of a solid varies, it means that the mass will change in relation to the volume. So, the correct answer is 3) Depends on the volume of the solid.