Correct Answer:
D. None of these
The correct answer is None of these. The SI (International System of Units) unit for speed is derived from the SI units for distance and time. The SI unit for distance is the meter (m), and the SI unit for time is the second (s). Therefore, the SI unit for speed is meters per second (m/s).
- Kilometers per hour (km/h) is a common unit for speed but not the SI unit.
- Miles per hour (mph) is a common unit for speed in some regions but not the SI unit.
- Centimeters per second (cm/s) is a unit of speed, but 'centi' is a prefix, and the base SI unit for length is the meter, not centimeter.