Which unit is primarily used to measure volumes in the metric system?

The unit primarily used to measure volumes in the metric system is liters. This is because liters, being a standard unit in the metric system, provide a clear and consistent way to quantify the volume of liquids and gases. One liter is defined as the volume of a cube that is 10 centimeters on each side, which relates directly to other metric units and provides ease of conversion within the metric system.

Cubic centimeters also serve as a valid metric unit for measuring volume, but they are often used for smaller measurements. This makes liters the preferred unit for larger volumes due to its practicality and common usage in everyday situations, such as in cooking or when measuring beverages.

While ounces are a unit of volume, they belong to the imperial system rather than the metric system. Milligrams measure mass rather than volume and do not apply to this context of volume measurement. Therefore, liters stand out as the primary metric unit utilized for measuring volume.