The correct option is B centrifugation
Particles with a very less difference in their densities are separated by centrifugation. This is because these particles do not separate on their own by the effect of gravity (i.e. sedimentation) due to a very tiny difference in their densities. Only substances having considerable or large difference in their density can be separated by sedimentation. Thus by spinning them at a very high rate in a centrifuge machine, the heavier particles are thrown away from the centre and stick on the walls of the centrifuge tube, whereas the lighter particles align themselves towards the centre. For example, water can be separated from all sorts of solids by this technique. Like, finely powdered charcoal mixed in water can be separated using centrifugation.