Which of the following best describes an emulsion?

An emulsion is best described as a homogeneous mixture of two substances that do not readily mix, typically oil and water. In an emulsion, tiny droplets of one liquid are dispersed in another, creating a stable mixture through the use of an emulsifier. This emulsification is critical in various cosmetic and pharmaceutical products, allowing for the combination of ingredients that would otherwise separate due to their different natures (e.g., oil and water).

The key feature of an emulsion is the mixture of immiscible liquids, which means they have different polarities and do not naturally blend together. The presence of an emulsifier helps to stabilize the mixture and prevent separation, resulting in a uniform appearance.

The other options refer to different types of mixtures: a mixture of soluble substances describes a solution, a solution of solid in liquid is a specific type of solution (not involving two liquids), and a suspension refers to solid particles dispersed in a liquid that can settle over time. None of these definitions capture the unique characteristic of emulsions, which is the combination of two unmixable liquids into a stable form.