The density measured by

Answer: Option A

The density of a substance is its mass per unit volume.
Mathematically, density can be represented as $$\mathbf{D}=\frac{\mathbf{Mass}}{\mathbf{Volume}}$$
For a pure substance, the density has the same numerical value as its mass concentration. Different materials usually have different densities and they may be relevant to buoyancy, purity, and packaging. The density of a material varies with temperature and pressure.