Which of the following is NOT an SI base unit?

• A. kelvin
• B. liter
• C. second
• D. kilogram

Answer: (B)

Verified step by step guidance

1. Recall that the International System of Units (SI) is based on seven fundamental base units, each representing a basic physical quantity.
2. Identify the SI base units: meter (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity).
3. Compare the given options to the list of SI base units: kelvin (temperature), second (time), kilogram (mass) are all SI base units.
4. Recognize that the liter is a unit of volume, which is derived from the meter (1 liter = 1 cubic decimeter), and is not an SI base unit itself.
5. Conclude that the liter is NOT an SI base unit, while the other options are.