What is the ratio of the mass of water to that of material at equal volumes?

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Question 36: "______ is the ratio of the mass of water to that of material at equal volumes"
This question defines a ratio of densities. Relative density (also known as specific gravity) is the ratio of the density of a substance to the density of a reference substance (usually water). While the phrasing "mass of water to that of material" is the inverse of the standard definition for specific gravity of solids ($G_s = \rho_{solid} / \rho_{water}$), it is the only option that represents a ratio of masses (or densities) of two different substances at equal volumes. The other options (humid density, dry density, saturation density) are all absolute densities (mass