Which statement describes the relationship between DomainResource and most resources?

• A. Most resources are derived from DomainResource
• B. DomainResource is a separate namespace and unrelated
• C. DomainResource is a subtype of Resource restricted to metadata
• D. DomainResource is deprecated

Answer: (A)

In FHIR, most resources share common features by deriving from a common intermediate class called DomainResource. This class adds things that are useful for everyday clinical data, such as a human-readable narrative (text), a way to include other resources inside a resource (contained), and the ability to attach additional information without changing the core structure (extension and modifierExtension). Because these capabilities are widely needed, many specific resources inherit from DomainResource, so they all automatically gain that shared set of fields and behaviors.

That’s why describing the relationship as most resources being derived from DomainResource is the best answer: it captures the standard inheritance pattern in the FHIR resource hierarchy. The alternatives are inaccurate because DomainResource is not a separate, unrelated namespace; it’s not merely a metadata-only subtype; and it’s not deprecated.