Attributes from an imported external audience are not ingested into the Profile and ExperienceEvent data stores within Adobe Experience Platform. They exist as a simple list of identities that qualify for a specific segment. Because these attributes are not part of the durable, time-series data in the unified profile, they cannot be combined with native Profile or Event attributes in the Segment Builder for creating more complex, stateful audiences. The external audience can be used as a whole (e.g., "profiles in Audience X"), but its internal attributes are not queryable.

A. The issue is more fundamental; external attributes cannot be combined with any native attributes (Profile or Event) because they are not part of the unified profile data model.

C. The Segment Builder UI is the primary tool for this task; a limitation to APIs only for such a common attribute type would be inconsistent with the platform's design.

D. This describes the standard data ingestion process for Profile and ExperienceEvent data, which is bypassed when importing a pre-computed external audience.

1. Adobe Experience Platform, Real-Time CDP Guide. "Import audiences". The documentation explains that importing an audience creates a segment membership but does not detail a process for ingesting the associated attributes into the unified profile for further segmentation. This implies the attributes are not durable or queryable in the same manner as native data. (Accessed via Adobe Experience League).

2. Adobe Experience Platform, Segmentation Service Guide. "Segmentation overview". This guide emphasizes that segmentation operates on data within the profile store (XDM Profile and ExperienceEvent classes). Data not in this store, like attributes from external segments, is not available for rule building. (Accessed via Adobe Experience League).