Which of the following describes a characteristic of a uniform composition?

A uniform composition refers to a mixture that has a consistent and even distribution of its components throughout. This characteristic is defined as a homogeneous mixture. In such mixtures, the individual substances that make up the mixture are indistinguishable from one another, often leading to a single phase. An example of a homogeneous mixture is vinegar in water, where the components are evenly mixed at the molecular level.

In contrast, a heterogeneous mixture presents a composition where the different components are not uniformly distributed, making it possible to distinguish between the various substances present. This could include mixtures like salad or oil and water.

The other terms, such as hygroscopic substances and viscous liquids, refer to specific properties of materials but do not describe the uniformity of their composition. A hygroscopic substance is one that can absorb moisture from the air, while a viscous liquid has a thick, sticky consistency. Neither of these terms pertains to the composition's uniformity in a mixture. Therefore, the characteristic that describes a uniform composition is correctly identified as a homogeneous mixture.