Which of the following is NOT a base unit of the International System of Units (SI)?

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

Answer: (A)

Verified step by step guidance

1. Understand that the International System of Units (SI) is based on seven fundamental base units, each representing a basic physical quantity.
2. Recall the seven SI base units: meter (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity).
3. Identify which units from the given options are part of these base units. For example, meter, second, and kelvin are all SI base units.
4. Recognize that the liter is a unit of volume, which is a derived unit in the SI system, not a base unit. It is related to the cubic meter (m³), which is the SI derived unit for volume.
5. Conclude that the liter is NOT a base unit of the SI system, while kelvin, meter, and second are base units.