Which RESTful Application Programming object can be used to organize the display of fields in an app?

The correct choice is a metadata extension, as it plays a crucial role in defining and organizing the display characteristics of fields within a RESTful application. In the context of SAP and other application development frameworks, metadata extensions allow developers to add or modify the metadata associated with existing data models. This includes details about how fields should be presented in the user interface, such as their order, visibility, and other display settings.

Using a metadata extension provides a flexible way to customize the user experience without altering the underlying data model directly. This approach separates presentation logic from the data structure, facilitating easier updates and maintenance of the application.

The other options, while relevant in the broader context of application design, do not specifically focus on the organization of field displays in an application. Service definitions are concerned with the overall service architecture, projection views focus on the subset of data a service can expose, and data model views typically refer to the structure of the data rather than its presentation within an application.