The best option for separating the two liquids that have formed a solution would be:
A. heating the liquids and letting one boil away first
This process is known as distillation and is effective for separating liquids based on their boiling points. If one liquid has a significantly lower boiling point than the other, it can be vaporized and collected, allowing for the separation of the components.
Option D, "Waiting for the two liquids to separate," is not applicable if they have formed a solution (which implies they are mixed at the molecular level). Option B and C are not suitable methods for separating mixed liquids in a solution, as they do not provide a systematic way to separate based on physical properties.