We check what physically happens inside a spinning washing machine drum against each option.
Diffusion is a slow, passive process where particles move from a region of higher concentration to lower concentration, it does not explain the forceful removal of water by spinning.
Reverse osmosis uses pressure across a semi-permeable membrane to purify water, a method used in water filters, not in washing machines.
Dialysis is a medical filtration technique for removing waste from blood, unrelated to clothes washing.
Centrifugation happens when the drum spins fast, creating an outward push on the water inside, forcing it through small holes in the drum while the clothes stay inside, becoming damp instead of soaking wet.
So option B, centrifugation, correctly describes the working of a washing machine.