Kilogram is the SI unit for mass.
The SI unit for mass in the metric system is the kilogram.
If, by 'metric system', you mean 'SI system', then the base unit for mass is the kilogram
The kilogram is the Base Unit (not 'basic' unit) in the SI system (not 'metric system') for mass.
In the metric system, the gram (g) is the named unit in the metric system which takes the various suffixes to measure larger or smaller amounts. However, the basic unit of mass in the SI system is the kilogram (1000g) which is used to define the size of a gram.
The SI unit of mass is the Kilogram.
In the SI - the current metric system - that would be the kilogram. In older metric systems, the gram has been used as the unit of mass.
The SI base unit for mass is the kilogram.
The metric standard unit of mass is the kilogram (Kg).
The kilogram is one of the 7 basic units of the SI (the current metric system).
The basic unit is the gram. The standard SI unit is the kilogram.
The SI (metric) unit for mass is the kilogram.
In the SI, that is the kilogram. (Older "metric systems" used the gram instead.)