Mass is a fundamental unit because it must be
larger than volume
calculated
measured
estimated

Measured

Explanation:

Mass is a fundamental quantity (not unit): this means that it is not derived from other quantities, therefore the mass of an object must be directly measured.

We can understand this better by comparing mass (a fundamental quantity) with density (a derived quantity). In fact:

- Mass is an intrinsec property of an object which represents the "amount of matter" in an object. It can be measured, for instance, using a scale. It is measured in kilograms (kg).

- Density is defined as the ratio between the mass (m) of an object and its volume, V:

As we can see, the definition of density contains two quantities, mass and volume. Therefore, density is not a fundamental quantity, but a derived quantity.