(i) → (b)

(ii) → (c)

(iii) → (d)

(iv) → (a)

Exp:

(i) A sol is a colloid made out of very small solid particles in a continuous liquid medium. Here the dispersion medium is liquid and the dispersed phase is liquid.

(ii) A gel is a solid jelly-like material that can have properties ranging from soft and weak to hard and tough. Here, in gels, dispersion of molecules of a liquid within a solid in which liquid particles are dispersed in the solid medium.

(iii) An emulsion is a special type of mixture made by combining two liquids that normally don't mix (immiscible).It is a colloid of two or more immiscible liquids where one liquid contains a dispersion of the other liquids. This process of turning a liquid mixture into an emulsion is called emulsification.

(iv) Foam is a colloidal system where the particles are gas bubbles and the medium is a liquid. Here the dispersion medium is liquid and the dispersed phase is gas. They are made by trapping air or gas bubbles inside a solid or liquid.