(i) Cyclohexane and n-octane both are non-polar. Hence, they mix completely in all proportions.(ii) KCl is an ionic compound while n-octane is non-polar. Hence, KCl will not dissolve at all in n-octane.(iii) CH$_3$OH and CH$_3$CN both are polar but CH$_3$CN is less polar than CH$_3$OH. As the solvent is non-polar, CH$_3$CN will dissolve more than CH$_3$OH in n-octane.Thus, the order of solubility will be KCl < CH$_3$OH < CH$_3$CN < Cyclohexane.