Which of these describes a solid?

A solid is characterized by having both a definite volume and a definite shape. This means that a solid retains its shape regardless of the container it's placed in, and its volume does not change. This property is due to the closely packed arrangement of particles in a solid, which vibrate in place but do not move freely. For example, a cube of ice has a specific shape and size that does not alter when placed in a larger container.

The other descriptions pertain to the properties of liquids and gases. A liquid has a definite volume like a solid, but it conforms to the shape of its container, which distinguishes it from the rigidity of a solid. A gas, on the other hand, has neither a definite volume nor a definite shape, as it expands to fill any container. The option implying a definite shape but no definite volume does not accurately reflect the behavior of solids or any common state of matter. Thus, the understanding that a solid maintains its structure in terms of both volume and shape clarifies why this choice is the correct one.