Answer : The SI unit to measure length is "meter".
Explanation :
SI unit means the international system of units. There are some fundamental units and some of the units are derived from fundamental units.
The SI units of some quantities are as follows :
- Mass : The SI unit of mass is Kilogram or Kg.
- Volume : The SI unit of volume of liter.
- Length : The SI unit of length is meter.
- Temperature : The SI unit of temperature is kelvin.
Hence, the correct option is (b) " meter ".