Answer:
D. units
Explanation:
A unit is the system in which a physical quantity is measured. It gives appropriate understanding of what physical quantity has been measured. All physical quantities have specific unit of measurements.
A unit can also represent the smallest part of a measurement. Example 1 unit, 2 units etc.
Since the unit of measurement is not indicated in the question, therefore 3, 090 would be represented using units. So that we have; 3, 090 units.