Which of the following is the metric unit for volume?

The metric unit for volume is liters. This is because the metric system is based on units of ten and is used globally for scientific and everyday measurements. Liters offer a standardized way to measure volume in various contexts, making them a fundamental unit in the metric system.

While ounces and gallons are both units of volume, they belong to the customary system used primarily in the United States and other countries, rather than the metric system. Kilometers, on the other hand, measure distance rather than volume. Thus, liters stand out as the appropriate metric unit for volume measurement.