Which of the following is NOT an SI base unit?

• A. liter (L)
• B. second (s)
• C. kelvin (K)
• D. meter (m)

Answer: (A)

Verified step by step guidance

1. Understand what SI base units are: SI base units are the fundamental units defined by the International System of Units from which all other units are derived. Examples include the second (s) for time, meter (m) for length, and kelvin (K) for temperature.
2. Review the given options: second (s), kelvin (K), meter (m), and liter (L). Identify which of these are recognized as SI base units.
3. Recall that the liter (L) is a unit of volume, which is not a base unit but a derived unit. It is related to the cubic meter (m³), which is the SI derived unit for volume.
4. Confirm that second (s), kelvin (K), and meter (m) are all SI base units representing time, temperature, and length respectively.
5. Conclude that the liter (L) is NOT an SI base unit because it is a derived unit for volume, not a fundamental base unit.