Try segregating the things around you as pure substances or mixtures.

(N/A) pure substance consists of only one type of particles,whereas a mixture contains two or more substances mixed in any proportion.
$(a)$ Common salt $(NaCl)$: Pure substance (it is a compound with a fixed chemical composition).
$(b)$ Soap: Mixture (it is a complex mixture of sodium or potassium salts of fatty acids,water,and additives).
$(c)$ Soil: Mixture (it contains sand,clay,organic matter,water,and air in varying proportions).
$(d)$ Rubber: Pure substance (natural rubber is a polymer of isoprene,$C_5H_8$,which is a single chemical compound).