Which tool should be used by an architectural designer to remove several families from a project to reduce file size?

To effectively reduce the file size of a Revit project, the most appropriate tool is the Purge Unused option. This tool is specifically designed to help users eliminate any families, materials, or other elements that are not currently being used in the project. When families are loaded into a Revit project but never actually utilized, they can unnecessarily increase the file size. Using the Purge Unused tool allows designers to efficiently streamline their project by removing these redundant elements without having to manually search for and delete each one.

In contrast, the other tools serve different purposes. Compact Central Model is used to make a central model file more compact but does not specifically target unused families. The Delete option is more manual and requires users to identify which families to remove, which could lead to the accidental deletion of in-use elements. The Audit tool is used to check and fix issues within a Revit model, but it does not focus on file size reduction through removing unused elements. Thus, Purge Unused stands out as the most effective choice for this task.