Components of which of the following substances cannot be separated easily?

Compound is a pure substance made up of two or more elements chemically combined in a fixed proportion by mass. Compounds cannot be separated into its constituents by simple physical method such as evaporation, filtration, distillation, solvent extraction or by using a magnet. Sugar (C₁₂H₂₂O₁₁) is a compound containing three elements carbon, hydrogen and oxygen in a fixed ratio by mass. Thus, it cannot be easily separated whereas ink, (dye in water), vinegar (acetic acid in water), seawater (water containing soluble salts) are mixtures and they can be easily separated by physical process. For example, dye can be separated from ink by evaporation, vinegar can be separated into its constituents by distillation. Moreover, salts can also be separated from seawater by evaporation.