What is a primary characteristic of a sub-assembly?

A primary characteristic of a sub-assembly is that it can be used in multiple main assemblies. This feature allows designers to create complex designs by grouping related components into a sub-assembly that can be reused across different assemblies. By using sub-assemblies, designers can streamline the assembly process and maintain consistency throughout their designs.

This approach is beneficial because it not only saves time when creating new assemblies but also enhances the manageability of the design by allowing changes to the sub-assembly to be automatically reflected in all the main assemblies that utilize it. This characteristic underscores the efficiency and flexibility of using sub-assemblies in 3D CAD modeling, such as in Solid Edge, making them valuable in intricate projects where components are shared among various products.

The other options do not align with the concept of a sub-assembly; for example, a sub-assembly can include multiple components, making it different from the notion of being a single standalone unit or only comprising one component. Additionally, the size of a sub-assembly relative to individual components does not serve as a defining characteristic.