What is the main cause of charge on a colloidal solution ?

Question

$\begin{array}{1 1}\text{(a) Due to adsorption of common ions of the non-electrolyte on the surface of the colloidal particles.}\\\text{(b) Due to adsorption of the electrolyte on the surface of the ionic particles.}\\\text{(c) Due to adsorption of common ions of the electrolyte on the surface of the colloidal particles.}\\\text{(d) None of these}\end{array}$