The correct answer is: B. Richter scale
The Richter scale is a logarithmic scale that measures the magnitude of earthquakes. It is based on the amplitude of seismic waves recorded by seismographs. The Richter scale is not a linear scale, so an earthquake with a magnitude of 7 is not twice as powerful as an earthquake with a magnitude of 6.
The Beaufort scale is a scale that measures the wind speed. It is based on the observed effects of the wind on the environment. The Beaufort scale is not a logarithmic scale, so a wind speed of 12 knots is not twice as strong as a wind speed of 6 knots.
The Mohs scale is a scale that measures the hardness of minerals. It is based on the ability of one mineral to scratch another mineral. The Mohs scale is not a logarithmic scale, so a mineral with a hardness of 7 is not twice as hard as a mineral with a hardness of 6.
Joules are a unit of energy. They are not used to measure the intensity of earthquakes.