The ratio of density of a substance to density of water at 4°C is usually referred as ___.

The ratio of density of a substance to density of water at 4°C is usually referred as ___.

The ratio of density of a substance to density of water at 4°C is usually referred as:

Which of the following statement(s) is/are true about relative density?
Statement 1: Relative density is known as the specific gravity of the substance.
Statement 2: Relative density of a substance is the ratio of the density of the substance to the density of water at $4^{\circ }C$.
Statement 3: Relative density of a substance is the ratio of the mass of water at $4^{\circ }C$ to the mass of a substance at $4^{\circ }C$.
Statement 4: Relative density is unitless.