Which document type represents an assembly in Autodesk Inventor?

The document type that represents an assembly in Autodesk Inventor is the .iam file. In the context of Autodesk Inventor, an assembly is defined as a collection of parts and subassemblies that are brought together to create a more complex structure or mechanism. The .iam file format is specifically designed to store information about how these individual parts and subassemblies are arranged, including their constraints and relationships with one another.

Other file types have different purposes: .ipt is used for individual part files, .idw is for creating 2D drawings of the models, and .ipn is used for presentations, which help in visualizing and demonstrating an assembly's parts in action. Each of these serves a unique role within the design process, but the .iam file is essential for defining the assembly itself, making it the correct choice for this question.