In the SI system, how is capacity (volume) expressed?

In the International System of Units (SI), capacity or volume is expressed in liters (litres). The liter is a fundamental unit for measuring the space occupied by substances, typically liquids. This measurement is essential in various fields, including engineering, chemistry, and everyday life, as it helps quantify how much of a substance is present.

The reason why this choice is the correct one is that liters are widely accepted and standardized for volume measurements in scientific contexts, making them a primary reference. This contrasts with other units; for instance, meters per second measures speed, joules measure energy, and liters per second indicates a flow rate rather than outright capacity. These other options do not measure volume directly, which reinforces the validity of liters as the appropriate answer.