Answer :
a mixture of alcohol and water is homogeneous as the solvent uniformly dissolves the solute present in it. while that of oil and water is heterogeneous as water and oil are two immiscible liquids that separate out in layers due to their varied densities which contain physically distinct parts.
A mixture of alcohol and water is homogeneous because it is having same or uniform compositiom or dissolution throughout the entire solution.Whereas oil and water are two immiscible liquids.They are having different densities.It is not having uniform composition throughout the solution.So it is heterogeneous.