Which three Theme Components are available out-of-the-box with the Universal Theme?

The Universal Theme in Oracle APEX includes a rich set of declarative components for building user interfaces. The Calendar, Comments, and Badge List are all standard, out-of-the-box UI components (region types or plug-ins) that are available for use in any application using the Universal Theme. They provide specific functionalities for displaying events, facilitating discussions, and presenting key metrics, respectively. REST Data Sources, however, is a data-layer component for defining connections to external services and is not a UI or "Theme Component."

D. REST Data Sources are a type of Shared Component used to define the connection and data operations for a REST API. It is a data-layer feature, not a visual theme component.

1. Oracle APEX App Builder User's Guide, Version 23.2, "Managing Regions". This guide lists and describes the various region types available, including Calendar (Section 9.5.1), Badge List (Section 9.5.1), and the Comments region plug-in.

2. Oracle APEX App Builder User's Guide, Version 23.2, "Managing REST Data Sources". This section (14.1) clearly defines REST Data Sources as a mechanism for managing data from external REST services, distinct from UI components.