How is a multi-body part created in Fusion 360?

A multi-body part in Fusion 360 is created by using multiple solid bodies within a single design file. This approach allows designers to create complex components by handling them as separate bodies that can interact with each other. Each solid body can be uniquely modified, combined, or subtracted from others to achieve the desired design. This method is particularly useful for modeling assemblies or parts that consist of multiple components without needing to create separate files for each one.

The other options, while related to the management of parts and assemblies, do not accurately describe how multi-body parts are specifically created. Duplicating bodies or importing files pertains to file management and organization but does not inherently lead to the creation of multi-body parts as understood in the context of a single design workspace. Additionally, linking parts from different assemblies refers to a method primarily used in managing larger projects rather than the actual creation of multi-body parts, which is the main focus of the question.