The correct answer is Centrifugation.

• The working principle of a washing machine is centrifugation.
• Centrifugation is a separation process that uses the action of centrifugal force to promote accelerated settling of particles in a solid-liquid mixture.
• Hence the correct answer is Centrifugation.

• Capillary-
  • Capillary action is the process of a liquid flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.
• Centrifugation-
  • Centrifugation is a technique used for the separation of particles from a solution according to their size, shape, density, viscosity of the medium and rotor speed.
  • The particles are suspended in a liquid medium and placed in a centrifuge tube.
  • The tube is then placed in a rotor and spun at a defined speed.
• Decantation
  • Decantation is a process for the separation of mixtures of immiscible liquids or of a liquid and a solid mixture such as a suspension.
• Diffusion
  • Diffusion is the net movement of anything from a region of higher concentration to a region of lower concentration.
  • Diffusion is driven by a gradient in concentration.