Which of the following materials can be classified as homogeneous?

The classification of materials as homogeneous refers to their consistency and uniformity in composition and properties throughout the material. Homogeneous materials are the same in all directions and at all points.

Plastics are a prime example of a homogeneous material. They are typically composed of synthetic polymers that create a uniform structure with consistent properties, such as strength, elasticity, and thermal conductivity. The uniform polymer chains and additives in plastics lead to predictable behavior under stress and similar responses to environmental conditions across the entire sample.

In contrast, concrete is a composite material made from aggregates (gravel, sand) and cement, leading to varying properties depending on the mixture and placement techniques. Wood consists of biological fibers which have natural variations in density and strength due to the tree's growth patterns, making it heterogeneous. Asphalt is a mixture of aggregates and bitumen, leading to varying properties depending on the proportions of these components. Therefore, the distinct structure and properties of plastics qualify them as homogeneous, making them the correct choice in this context.