The correct answer is: C. specific gravity
Specific gravity is a dimensionless quantity defined as the ratio of the density of a substance to the density of a standard substance. The standard substance is usually water at a temperature of 4 °C (39.2 °F).
In this case, the density of the liquid is 850 kg/m^3. The density of water at 4 °C is 1000 kg/m^3. Therefore, the specific gravity of the liquid is 0.85.
Specific weight is the weight of a unit volume of a substance. It is calculated by multiplying the density of a substance by the acceleration due to gravity.
Specific mass is the mass of a unit volume of a substance. It is calculated by dividing the density of a substance by the acceleration due to gravity.
Specific density is the density of a substance relative to the density of water at 4 °C. It is calculated by dividing the density of a substance by the density of water at 4 °C.