(i) → (d)

(ii) → (c)

(iii) → (a)

(iv) → (b)

EXPLANATION:

(i) Butter is an example of dispersion of liquid in solid as the dispersed phase is solid and dispersion medium is liquid.

(ii) Pumice stone is an example of dispersion of gas in solid as the dispersed phase is gas and dispersion medium is solid. Here, dispersion of gas takes place and the gas bubbles are pierced within the solid particles.

(iii) Milk is an example of dispersion of liquid in liquid as the dispersed phase is liquid and dispersion medium is liquid.

(iv) Paints are an example of dispersion of solid in liquid as the dispersed phase is solid and dispersion medium is liquid.