Milk is a type of colloidal solution (emulsion) in which both dispersed phase and dispersion medium are liquid.
i.e., liquid fats are dispersed in water.
Note : Foam is an example of gas dispersed in liquid dispersion medium.
Sols in water do not form a colloidal solution but form a true solution.
Sugar in water do not form a colloidal solution but form a true solution.
So, The correct option of this question is (A).