Which of the following is an example of a homogeneous mixture of solids?

A homogeneous mixture of solids is one where the components are thoroughly mixed at a microscopic level, resulting in a uniform composition throughout the material.

Metal alloys serve as quintessential examples of homogeneous mixtures of solids because they are formed by melting and mixing different metal elements, which then solidify into a single phase. The distribution of the constituent metals is consistent and uniform throughout the alloy, making it a true homogeneous substance.

In contrast, while wood is a natural composite made of various organic materials and fibers, it cannot be classified as homogeneous due to its varying structures and compositions. Concrete, on the other hand, is made up of aggregates, cement, and water; while it seems uniform, it still maintains distinct components on a microscopic level. Plastic, while often uniform in its properties, can be a polymer with additives that may not always distribute evenly, further disqualifying it from being labeled as a homogeneous mixture of solids.

Thus, metal alloys are the clear choice for being a homogeneous mixture of solids due to their uniform composition and properties that arise from the thorough blending of metal elements.