What technique separates mixtures of liquids with varying boiling points?

The correct choice for separating mixtures of liquids with varying boiling points is fractional distillation. This technique is particularly effective for separating components of a mixture when their boiling points are closer together, typically within 25 degrees Celsius.

Fractional distillation utilizes a fractionating column, which provides surface area for multiple vaporization and condensation cycles as the mixture is heated. As the mixture boils, the component with the lower boiling point vaporizes first and rises through the column, condensing back into liquid on the surfaces within the column as it cools, while the higher boiling point liquid remains below. This process allows for better separation than simple distillation when dealing with relatively close boiling points.

In contrast, simple distillation is best suited for separating liquids with significantly different boiling points, typically greater than 25 degrees Celsius. While evaporation is a method for removing a solvent from a solution, it is not effective for separating liquid mixtures. Filtration is used for separating solids from liquids or gases but does not apply to the separation of liquid mixtures. Thus, fractional distillation is the most appropriate choice for the situation described.