Which of the following is a characteristic of an aqueous solution?

The characteristic of an aqueous solution that makes it stand out is its ability to be soluble in water. An aqueous solution is, by definition, a solution where water is the solvent. This inherent property allows various substances to dissolve in water, facilitating numerous biological and chemical processes.

Aqueous solutions are crucial in many applications, including pharmaceuticals and biological systems, where substances need to be dissolved for absorption, transportation, or reaction. The solubility of a solute in water signifies that it interacts well with water molecules, often forming hydrogen bonds or other interactions that lead to dissolution.

The other characteristics listed do not apply to aqueous solutions in the same way. For instance, high viscosity is typically associated with more concentrated solutions or certain types of liquids but is not a defining feature of aqueous solutions. A low melting point does not pertain directly to the concept of aqueous solutions either, as it relates more to the physical properties of substances rather than their solubility in water. Lastly, being soluble in lipids is a property of lipophilic substances, which would not pertain to the characteristics of an aqueous solution where water is the dominant solvent.