Explanation

(c)
(i)Dialysis is the method of separating particles of colloids from those of crystalloids by diffusion of mixture through perchament membrane.
(ii)Ultrafiltration is the method of separating particles of electrolyte from colloidal particle by filtering through ultrafilter paper.
(iii)Electrophoresis is the movement of colloidal particles under influence of electric field.
(iv) Peptization is a process of passing of precipitate into colloidal particle on addition of suitable electrolyte.
$\therefore$ Peptization is correct answer.